Tang Ming became the main currency in circulation in the middle and late period. In fact, silver began to circulate in the Song Dynasty, but its circulation scope was very limited. The payment of silver is mainly used for foreign economic exchanges, because most countries with economic relations with China use silver. Looking for the confrontation between the Northern Song Dynasty and the Liao regime and Xixia regime, in order to obtain the peace of the northern border, silk and silver were continuously paid to the Liao and Xia dynasties. However, why do the Khitan, Nuzhen, Mongolia and other ethnic groups want silver instead of gold? Because they have trade with the western regions, and the western regions spread silver. Therefore, the popularity of silver in the Song Dynasty was influenced by Central Asia. Not only that, the imperial court also began to use silver in the payment of official salaries and military salaries, but in daily folk transactions, silver is still not much. In the middle and late Ming Dynasty, due to the massive inflow of silver from America, silver really became the main currency of society. It was not until 1935 that the Kuomintang government implemented the legal tender policy and abandoned the silver standard system that this situation was stopped. So far, silver has existed as the main currency for 500 years.