In order to define the concept of customary law scientifically and make it clear that customary law plays an important part in legal modernization of China, Marxist dialectical materialism as a basic method of research is adopted in the article. In addition to it, lots of methods such as process analysis, historical analysis and comparative analysis are also applied. Generation, evolution and status of customary law, the relationship between customary law and national law, and role of customary law in the m...