The spot dealer delivers the goods that meet the delivery standard to the delivery warehouse of the exchange. After the delivery warehouse is qualified, it will issue a standard warehouse receipt to the holder, who will go through the registration formalities with the delivery department of the exchange. Only registered warehouse receipts can be delivered, and the total quantity is the inventory quantity announced by the exchange. The registered warehouse receipt can also be cancelled, but at this time, the goods marked by the warehouse receipt may not have left the warehouse, and may still be in the delivery inventory. When the contract is delivered in a certain month, some warehouse receipts will be cancelled for delivery, because some warehouse receipts will enter the spot market for each delivery. But sometimes, in order to influence the price, the makers (or the main holders of warehouse receipts) who participate in futures trading will change the inventory quantity announced by the exchange by registering or canceling warehouse receipts. For example, when the main force wants the price to rise, a large number of registered warehouse receipts are cancelled, which leads to the shortage of deliverable goods, which leads to traders' expectation of future prices, but in fact, deliverable goods have not decreased and are still stored in the warehouse. When the main force hopes that the price will fall, it will register to open a position again [1], which will lead to an increase in goods, thus causing the futures price to fall.