The fuse mechanism is used to limit the fluctuation of stock index futures, which is a means adopted by the exchange to control risks when the stock index futures market fluctuates greatly: when the fluctuation reaches the fuse point specified by the exchange, the exchange will suspend trading for a period of time, then start normal trading and reset the next fuse point. The fuse price of Shanghai and Shenzhen 300 index futures contracts is 6% of the settlement price of the previous trading day. When the market price reaches 6% and lasts for 1 min, the fuse mechanism starts. In the following 10 minutes, the declared price of buying and selling can only be less than 6%, and the transaction will continue, and the declaration exceeding 6% will be rejected. After 10 minutes, the price limit will be enlarged to 10%.