← Back to Blog · 2026-10-06 · 7 min read · Market Preview

It's 9:00 a.m. Shanghai time. Rebar futures open up 1.2% on strong volume, and your feed is full of bullish chatter. But your spot quote from a Tangshan steel market tracker shows physical rebar prices barely moved. Futures are running; the physical market is shrugging. Most traders take the futures move at face value. Experienced China futures traders look at that gap — the basis — and ask a different question: which side is wrong, and which side will move to close the gap?

That question is the entire foundation of basis trading in Chinese commodity futures. And for rebar and iron ore — arguably the two most actively watched contracts on Chinese exchanges — the spot-futures gap is one of the cleanest short-term signals you'll find anywhere. Let's break down how it works, what the contracts actually look like, and how to turn it into a repeatable process.

What Basis Actually Is (and Why It's Not Just a Textbook Word)

Basis is simply:

Basis = Spot price − Futures price

When spot is above futures, you have a positive basis (futures trading at a discount — a backwardated structure). When futures are above spot, you have a negative basis (futures at a premium — a contango-like structure).

Here's the part that matters: futures contracts have an expiry date, and at expiry, futures must converge to the physical price. That's not a theory — it's enforced by the delivery mechanism. So the basis is a rubber band. Stretch it far enough in either direction, and one of two things happens: futures move back toward spot, or spot moves toward futures. Usually it's a combination. Your job as a short-term trader is to figure out which side has the energy.

In Western markets, basis is dominated by institutional hedgers and storage economics. In China, it's something different — and that's exactly why it's so useful.

Why Basis Works Differently in China

Chinese commodity futures markets have a structural feature that amplifies basis signals: the futures pits are heavily retail and speculative, while the spot market is driven by physical reality — steel mills, traders, construction sites, and inventories.

What that means in practice: futures can detach from spot on pure sentiment, leverage, or policy headlines, sometimes dramatically. The spot market, meanwhile, moves on actual orders, mill production schedules, and warehouse inventories. When sentiment and reality diverge, the basis blows out — and convergence eventually pulls everything back together.

You've seen this movie before at market level. During the 2021 thermal coal rally, Chinese coal futures roughly tripled in a matter of months while spot supply tightened, and when Beijing stepped in with intervention measures around October 2021, futures collapsed violently back toward physical reality. The 2020 oil crash — where WTI briefly went negative on delivery-mechanics pressure — taught the same lesson globally: futures are paper, spot is physics, and the gap between them is where risk and opportunity live.

Rebar and iron ore are the classic pair for watching this in China, because they're linked by steel mill economics. Roughly speaking: mill margin ≈ rebar price − (iron ore and coking coal costs + processing costs). When rebar futures run hot relative to spot while iron ore lags, mills get an implied profit boost on paper — which encourages more production, which eventually pressures spot rebar. The basis relationships between the two contracts encode this entire industrial feedback loop.

Know Your Instruments: Rebar and Iron Ore Contract Specs

If you're going to trade rebar and iron ore, you need the actual specs burned into memory. Here's the table:

Two practical notes. First, iron ore's night session means the contract reacts to overnight news — including Singapore iron ore swaps and Chinese policy announcements — before the spot market even opens. Second, always check current margin rates and position limits directly with the exchange or your broker; Chinese regulators adjust these frequently, especially when a market gets hot, and the rules as of any given month are the only ones that matter.

The Three Basis Signals That Matter for Short-Term Trading

Signal 1: The Stretched Futures Premium

When rebar or iron ore futures push to a large premium over spot — say the basis goes meaningfully negative and stays there — you're looking at speculative froth. Physical buyers haven't confirmed the move. Historically, extreme futures premiums in these markets have tended to mean-revert within days to weeks, either through futures pulling back or a delayed spot catch-up. The trigger is often mundane: rising exchange inventories of warehouse receipts, soft daily transaction data from steel trading hubs, or a policy headline that punctures sentiment.

The 2016–2017 period after China's supply-side reform kicked off is a good study: rebar and iron ore futures went through repeated sentiment-driven surges and pullbacks as speculative money flooded in, and the basis repeatedly acted as the reality check.

Signal 2: Basis Convergence Direction

Don't just look at the level of the basis — look at the rate of change. A basis narrowing because futures are falling while spot holds is bearish confirmation for futures. A basis narrowing because spot is rallying to meet futures is a demand signal — often the start of a genuine physical-market-driven leg up. Same gap, two completely different trades. Track daily: is the rubber band snapping back from the futures side or the spot side?

Signal 3: The Mill Margin Cross-Check

Before acting on a rebar basis signal, check what iron ore is doing. If rebar futures are at a premium but iron ore futures are also bid, mill margins on paper aren't expanding much — the bullish rebar signal is weaker. If rebar futures are bid while iron ore futures sit flat or discount, implied mill margins are expanding, which historically incentivizes higher production and eventually weighs on spot rebar. The pair trade tells you more than either contract alone.

A Practical Framework You Can Actually Run

Here's a concrete daily process. No indicators you can't build in a spreadsheet:

• Pull spot quotes every morning. For rebar, use a published spot price for a major hub (Beijing or Shanghai HRB400 20mm rebar is the standard reference). For iron ore, track a published 62% Fe fines index or imported ore port price. Consistency matters more than the exact source — use the same reference every day.
• Compute basis as a percentage, not an absolute number. Basis ÷ spot × 100. A ¥100 basis means something very different at ¥3,500 rebar versus ¥4,500 rebar.
• Build a rolling baseline. Track the 20-day average and standard deviation of your basis-percentage series. When the current basis stretches beyond roughly two standard deviations from the mean, you're in signal territory.
• Classify the divergence. Futures premium + flat spot = fading candidate. Futures discount + firm spot = strength confirmation. Note which side is moving to close the gap each day.
• Check the cross-market. Before entering on a rebar signal, glance at iron ore (and ideally coking coal) for the mill-margin context described above.
• Respect the calendar. Chinese demand is seasonal: the March–April construction peak and the September–October window are historically the strong periods; winter heating-season production restrictions and the weeks around Chinese New Year distort both spot activity and futures positioning. A basis signal that appears right before Golden Week or a major policy meeting carries different risk than one in a quiet stretch.
• Define invalidation. If the basis keeps stretching against your position rather than mean-reverting within your expected window, the market is telling you the spot side is repricing — get out and reassess. Basis trades are convergence trades; if convergence isn't happening, the thesis is dead.

Position sizing note: iron ore at 100 tonnes per lot and a ¥0.50 tick gives you ¥50 of P&L per tick per lot — it moves fast. Rebar at 10 tonnes and ¥1 tick is ¥10 per tick. Size accordingly, and remember that Chinese exchanges can raise margins or trading limits overnight during volatile stretches, which directly changes your effective leverage.

The Risks That Kill Basis Trades

Be honest about what can go wrong:

• Policy risk is the big one. Chinese authorities actively intervene in commodity markets when prices run — through margin hikes, position limits, trading restrictions, and verbal guidance. A basis signal that looks perfect can be invalidated by a single announcement. Never assume policy is neutral.
• Convergence takes time. The rubber band snaps at expiry by definition, but your margin account lives in the present. A stretched basis can stretch further for weeks before reverting.
• Spot data quality. Spot quotes can lag or vary by region and quality spec. Use a consistent, published reference and understand its basis for delivery standards.
• Delivery mechanics near expiry. As contracts approach the delivery month, the rules that govern physical delivery — quality premia/discounts, warehouse receipt availability — start dominating pricing. If you're not set up for delivery, exit well before then.

Putting It to Work

Basis trading isn't a holy grail — it's a lens. It tells you when the paper market and the physical market disagree, and disagreement is where short-term edge lives. In Chinese commodity futures, where speculative flow and industrial reality regularly part ways, that lens is sharper than almost anywhere else. Start by simply logging the rebar and iron ore basis every day for a month. You'll quickly develop a feel for what "normal" looks like and when the band is stretching.

And when you're ready to test whether your basis framework actually holds up under pressure, you can run it against real China futures market data in a structured evaluation at XS Select — starting from $29. It's the cheapest tuition you'll ever pay on the gap between what futures are doing and what the physical market knows.