Common law traditionally contains the formal rationality of commercial law. According to common law tradition, there is no possibility of preventing commercial law from being formalized. Formalization of commercial law in common law system is an institutional demand of market economy and is jointly promoted by the legal tradition of common law countries. The commercial law in the two legal systems indicates that the commercial law is made depending on the market economy and the form of commercial law is restricted by legal tradition. The formalization and assimilation of commercial law are an internal need as well as an inevitable trend in the course of economic development.