After the mid-Ming Dynasty, the social economy and commodity currency economy developed greatly, and Daming paper money withdrew from the circulation field due to serious devaluation. Silver, with its natural characteristics of small size, great value, easy separation, casting and portability, gradually became the dominant currency in circulation after Tianshun, and the monetary status of silver in Qin Long was recognized by the state in the early days. Silver is the main currency in various currencies (copper coins, iron coins, lead and tin coins, silver coins, etc.). ), and the ultimate function of all currencies is expressed in silver. When other currencies encounter such problems in circulation, it is difficult to travel and the circulation is not smooth, but silver is a commodity and wealth that everyone welcomes and desperately wants to obtain, that is, legal tender. During the Wanli period, Zhang carried out the "one whip method" nationwide, which marked the final completion of silver monetization. On the other hand, in the process of silver monetization, taxes gradually moved towards the road of "only collecting silver" and "not collecting money", which promoted the reform of the national tax system and made it possible for the Ming Dynasty to collect silver in the form of taxes nationwide.

Silver is a weighing currency, with two as the basic unit. People usually divide silver into three types according to its shape, crushing degree and use: one is broken silver, that is, one or two pieces of loose silver, whose shape and weight are not standardized, and there are names such as dripping water and praying beads; The second is silver ingots; The third is the silver dollar, which is the silver coin that flows into China from foreign countries, mainly circulating in Fujian and Guangxi. Foreign silver dollars flowing into China also have the problem of insufficient color. The records in Zhang Xie's "A Western Examination of Oriental Ocean" show that the problem of silver dollar's quality is serious, especially in the late Qing Dynasty. In China, foreign businessmen often exchange 90% or even 70% silver dollars for 100% silver ingots. Specific to the actual situation in China in the Ming Dynasty, silver dollars were not used to pay taxes. Silver ingots were a form of "coinage" in China at that time, but we must make it clear that this form of coinage was not minted by the state, but by silversmiths all over the country or by silversmiths under the supervision of the government. The time, place, weight and silversmith's name engraved on it do not have the legal effect of the national legal tender seal. This is the so-called banking system. This kind of silver ingot is not a coin, and it has institutional defects. In Adam Smith's time, it was pointed out that this strip currency had two major institutional defects: inconvenient weighing and difficult testing. Until the 1930s and 1940s, Keynes still said: "China used silver as the standard of value, but generally speaking, silver was only recently minted."

Gu Qian-liang's Poems argues that there are two disadvantages in using silver as currency: paying land tax with silver makes the folk silver "consume the day" and "the valley is cheap and the people are poor"; In exchange for silver, "silver is light and easy to buy" will further encourage the greed of corrupt officials and thieves.

Originally our country was short of money. The Imperial Classics Collection (Volume 299) said: "The emperor is worried about the shortage, the food of cloth and silk is insufficient, and the silver is insufficient." In the early years of Kangxi, Mu, who opposed the maritime ban, expressed the hidden worry that the silver shortage was coming: "However, there are two sources of silver: one is silver mines, and the other is silver boats." Because mining has stopped, there are no proper requirements for pit metallurgy. Since moving the sea is strict, sails are not allowed to go abroad. "If both ways of producing silver are dead, only silver is circulating in the province now." Farmers are not money holders in both silver-producing areas and non-silver-producing areas, so they have to turn their agricultural products into silver. This link will definitely make farmers suffer losses in their interests.

Only when the people have money in their hands can they complete the taxes required by the state. From the perspective of technical operation, it is almost impossible for ancient countries to collect taxes directly from households, and in this process, an agent class will inevitably emerge gradually. The tax collection is mainly carried out by Baotou or blue lagoon. Usually Baotou or blue lagoon is filled by local big families, rich families or local powerful families. Baotou or households will collect taxes from a certain number of households or households within a certain range, and they will pay them to the local government. The reason why they are willing to undertake local tax collection affairs is entirely out of the consideration of obtaining profits. In every step of paying taxes to local governments, people will be exploited at different levels and suffer much damage.