Stock index futures have the function of price discovery. The futures market is extremely liquid because of its low margin and low transaction costs. Once there is information that affects everyone's expectations of the market, it will be quickly reflected in the futures market. And can be quickly transmitted to the spot market, so that the spot market price reaches equilibrium. Stock index futures II has the function of risk transfer. The introduction of stock index futures provides a way for the market to hedge risks, and the risk transfer of futures is realized through hedging. If investors hold stocks related to stock indexes, they can sell stock index futures contracts in order to prevent losses caused by future declines, that is, when the short positions of stock index futures match the long positions of stocks, investors avoid the risk of total positions. Stock index futures are beneficial for investors to rationally allocate assets. If investors only want to get the average return of the stock market, or are optimistic about a certain kind of stocks, such as technology stocks, if they all buy in the stock spot market, they will undoubtedly need a lot of money. However, if they buy stock index futures, they can track the market index or the corresponding technology stock index with only a small amount of money to achieve the purpose of sharing market profits. Moreover, stock index futures have a short term (usually three months) and strong liquidity, which is beneficial for investors to quickly change their asset structure and rationally allocate resources. In addition, stock index futures provide new investment and speculative varieties for the market; Stock index futures also have arbitrage function. When the market price of stock index futures deviates greatly from its reasonable pricing, there will be arbitrage activities of stock index futures. The introduction of stock index futures also helps state-owned enterprises to directly raise funds in the securities market; Stock index futures can slow down the impact of fund cashing on the stock market. Stock index futures provide a new means for risk management of securities investment. It changed the basic mode of stock investment from two aspects. On the one hand, investors have direct means of risk management, and portfolio risk can be controlled within the floating range through index futures. On the other hand, stock index futures ensure that investors can grasp the opportunity to enter the market in order to accurately implement their investment strategies. Take the fund as an example. When there is a short-term depression in the market, the fund can seize the opportunity to leave with the help of stock index futures without giving up the stocks to be invested for a long time. Similarly, when there is a new investment direction in the market, the fund can seize the opportunity and calmly choose individual stocks. It is precisely because the role of stock index futures in active risk management strategy is more and more accepted by the market that in the past twenty years, stock exchanges all over the world have launched this trading variety for investors to choose from. The function of stock index futures can be summarized as four points. 1. Avoid system risks. 2. An active stock market. 3. Diversify investment risks. 4. You can hedge.