In stock index futures trading, the risk brought by the inconsistency between spot price and futures price and the uncertainty of basis fluctuation is called basis risk. If the basis changes in a favorable direction, not only can better hedging effect be achieved, but also additional profits can be obtained; On the contrary, it will not only affect the hedging effect, but even suffer losses. For example, when buying hedging, investors may make profits by buying low and selling high when the basis becomes weak, that is, the spot price is relatively low and the futures price is relatively high, because they want to buy spot and sell futures contracts at the end of hedging. On the contrary, if hedging is sold at this time, investors may have to sell the spot and buy futures contracts at the end of hedging, thus losing money by selling low and buying high when the basis becomes weak.