It is to buy (sell) a stock index futures contract that is equal to or close to the spot market amount of the stock, but in the opposite direction, so as to compensate the actual price risk brought by the price change of the spot market of the stock by selling (buying) the futures contract at some future time. The most basic types of hedging can be divided into buying hedging and selling hedging. Buying hedging refers to buying stock index futures contracts through the futures market to prevent losses due to the rise in spot prices of stocks; Selling hedging refers to selling stock index futures contracts through the futures market to prevent losses caused by falling spot prices of stocks. Hedging is the driving force of the futures market. Whether it is commodity futures market or financial futures market, it comes from the spontaneous trading behavior of buying and selling forward contracts in the process of production, operation or financial investment, when facing the risks brought by the sharp fluctuation of spot prices. The trading mechanism of this forward contract has been continuously improved, such as standardizing the contract, introducing hedging mechanism and establishing margin system, thus forming modern futures trading. Commercial enterprises purchase insurance for production and operation through the futures market, which ensures the sustainable development of production and operation activities. However, financial enterprises can avoid and resolve the systemic risks in the stock market through hedging transactions in the stock index futures market. The word "speculation" used in futures trading is not a derogatory term, but a neutral word, which refers to the trading behavior of grasping the opportunity according to the judgment of the market and making use of the price difference in the market to profit from it. Speculators can "short" or "short". The purpose of speculation is very direct, that is, to obtain the profit of price difference. But speculation is risky.