The introduction of stock index futures is unfavorable to small and medium investors to a certain extent, because institutions and large households can lock their positions in the spot market by selling stock index futures contracts in the futures market. Because the futures market and the stock market interact, they can sell their own stocks, so that the market will fall, and then their futures contracts in the futures market will make money. This phenomenon may exist, but there will always be differences in the market, and shorting the stock index also needs to find an opponent. It is impossible to operate in this way, and if it is not operated properly, it may cause great losses. If the stock market falls after the introduction of stock index futures, it is a good time to buy.