As a tool for price discovery, stock index futures open 15 minutes earlier than the stock market, which is beneficial to price discovery of all parties in the market. And the closing time is 15 minutes later than the stock market, because it will take some time to digest the liquidity and let the market make an estimate of the next day's price, so as to better play the price discovery function. This design is more conducive to the futures market to reflect the stock market information, and it is convenient for investors to use stock index futures to manage risks.