In futures trading, any trader must pay a certain proportion (usually 5- 10%) of the value of the futures contract he buys and sells as the fund guarantee for the performance of the futures contract, and then he can participate in the futures contract trading and decide whether to add funds according to the price change. This system is the deposit system, and the funds paid are the deposit. The margin system not only embodies the unique "leverage effect" of futures trading, but also becomes an important means for the exchange to control the risk of futures trading.