When the futures contract expires, the futures price should be the same as the spot price, otherwise there will be risk-free arbitrage opportunities (for example, when the futures price is higher than the spot price, the arbitrageur can buy the spot in the spot market, then register it as a warehouse receipt and get it delivered in the futures market. Because of the existence of arbitrageurs, the spot market may rise because arbitrageurs buy more (the price of goods in oversupply will remain unchanged or rise slightly), while the futures market will be thrown out because of the large number of arbitrageurs. Before the expiration date of futures contracts, futures and spot are not only affected by the relationship between supply and demand, but also by the cost of arbitrage. The factors affecting futures prices are basically the same as those affecting spot market prices. Therefore, futures prices and spot prices will show a positive correlation trend most of the time. In the futures market with the same trading volume as the spot market, whether the futures price is ahead of the spot price or the spot price is ahead of the futures price, the sample research results of different commodities, different countries and different periods are inconsistent. Due to the different market structure and legal restrictions of various commodities, the function and adequacy of the futures market to reflect the changes in spot supply and demand are also different. But generally speaking, the futures market is more responsive to information. Because the spot market needs huge funds, even if it involves real factors such as ownership and control, the long and short power is limited and it is impossible to get a complete response. These limited forces can be fully exerted in the futures market, so the futures market has the function of price discovery. In addition to the factors that affect the spot price, futures are also affected by the following factors: (1) The cost of holding the spot, including the capital cost of purchasing the spot, warehousing cost, insurance cost, etc. (2) Gains from holding cash, such as cash dividends and convenience fruits. (3) Expectation psychology of future supply and demand. (4) Seasonal factors. These factors are the fundamental factors that cause the fluctuation of basis. When analyzing futures prices, we should not only consider all the factors of spot market price fluctuation, but also consider the changes of the above factors.

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