First of all, Jiaozi used in the Song Dynasty adapted to the economic development at that time and was mainly used for commodity exchange. Secondly, due to the inconvenient transportation at that time, the circulation scope was limited; In addition, because paper money is easy to carry and has low storage cost, it is more suitable for small-scale economic exchanges. However, in today's social environment, as the main currency in the world, the use and influence of the US dollar have gone far beyond the scope of a single country or region and become an important part of the global economic system. Its role is not limited to the trade field, but also involves the influence of financial markets, foreign exchange policies and other aspects. Therefore, the difference between the two lies in the different background and economic environment, and the degree of correlation between RMB and the world economy is completely different.