Abstract: Dao and Law are two important concepts of classical Chinese philosophy.In the middle Warring States,they were integrated in Huang-Lao school,which lead to thought tendency that used Dao to expound Law,with the coming up of the "Dao generating Law" concept as the focus.In "Dao generating law" concept,Dao is the essence of law,meanwhile law is the manifestation of Dao,and law must operate under the principles of Dao.Law aims to take human and other things back to Dao,so there is a relationship of substance and phenomenon between Dao and Law.The sage-monarchs holding fast to Dao is the medium between Dao and Law and the real legislator,therefore he should be restrained by Dao and Law.