The essence of stock index futures trading is a process in which investors transfer their expected risk of the whole stock market price index to the futures market, and the risk is offset by the trading operations of investors who have different judgments on the stock market trend. Like stock futures trading, it belongs to futures trading, except that the object of stock index futures trading is stock index, which is based on the change of stock index and settled in cash. There are no real stocks on both sides, only stock index futures contracts can be bought and sold at any time.