Futures margin is collected by the exchange from both parties. Before the expiration of the contract, as long as the deposit is paid in full, both parties can sell short and do not need to be qualified for physical delivery. In the modern financial system, margin trading is widespread, as well as margin foreign exchange, gold deferred trading and swap trading. Because speculators can enlarge the transaction amount through margin trading, it is also called leveraged trading. The core of modern financial system is credit. Although futures trading is not a complete credit transaction, it has the characteristics of credit transaction through hierarchical settlement and margin mechanism, which enlarges the transaction amount and reduces the transaction cost, thus promoting the overall activity of the market. Margin trading will inevitably bring the potential risk that the losses cannot be fully paid.