Abstract: The legal interest boundary of law is basically consistent with the extension boundary in logic,and it is often the legal interest boundary of a specific law in the legal system in a broad sense that determines its extension boundary.At the national level,national law and folk law constitute the basic law form of the legal system in a broad sense.The legal interest boundary of national law aims to protect the legal interests of political order within the scope of the country,and determines that its extension boundary is the source forms of specific laws such as constitution,criminal law,civil law,administrative law and so on.With reference to the boundary of national law,the legal interest boundary of folk law aims to protect the legal interests of public order in different regions or fields within the scope of the country,that is,the legal interests of public order in various fields,and determines that its extension boundaries are national law,rural law,guild law,and various customary laws (including taboos,habits,customs,etiquette,etc.).The determination of the specific connotation of the boundary of folk law has its specific legal philosophy basis,and the logic of public order in the field determines the legal interest boundary and extension boundary of folk law,which is the basic legal basis to clarify the boundary of folk law.

Key words: folk law, legal interest boundary, national law, philosophy of right