Spot price and futures price are interactive. Futures price has the function of finding forward spot price, but it will be limited by spot price when it expires, which leads to the convergence of the two prices on the last trading day. The two most important functions of the futures market are to avoid risks and find prices, which involves hedging. Two of the economic principles are that futures prices are consistent with spot prices, and futures prices and spot prices tend to be consistent with contract expiration dates. Therefore, there are also cases where the forward futures price is higher than the recent futures price. When the futures contract approaches the delivery date, the determinants of the two prices are almost the same. Otherwise, the existence of the spread will make arbitrageurs have a trail to follow.