Traditional theory: futures price = spot price+holding cost+premium, etc. According to the delivery date and storage and transportation cost, the holding cost+premium can be roughly calculated. If the total holding and delivery cost of Shanghai T+D is 100 for the contract between silver futures 1406 and spot silver, the price of futures 1406 should theoretically be higher than TD 100. If the futures price is higher than TD 150 due to market fluctuation on a certain day, you can buy TD and sell futures. When the delivery date is up, you can use TD to collect the spot and deliver it to the futures to fulfill the contract. Cost 100 point, price difference 150 point, you can get a risk-free profit of 50 points.

Now, after the opening of futures night trading, arbitrage trading can be realized through liquidation operation without delivery. There is an assumption that futures and spot prices will remain balanced in the short term. If the spread deviates, you can open positions in the opposite direction synchronously and get arbitrage profits after the spread returns. As mentioned above, if the price difference between futures 1406 and TD is 100 in a short time, and if the market suddenly changes one day and the price difference becomes 120, you can short the futures for more TD, and close your position when the price difference returns to 100, with a gross profit of 20 points and a handling fee of about 5 points. This kind of arbitrage transaction is convenient and concise, with low risk and stable income.