Futures trading. In the trading mode of the national debt circulation market, the buyers and sellers of national debt have agreed on the price and trading varieties in advance, and it is necessary to discuss and determine the trading time and scale in advance. Therefore, the buyers and sellers of public bonds agree in advance on the price and trading varieties as futures trading. Public debt refers to a formatted debt certificate issued by the government to investors in order to raise financial funds according to certain procedures, and promises to pay interest and repay the principal within a certain period of time.