The innovation policy has direct affection on the function of national innovation system and has great impact on its performance.There is close relationship between innovation policy and national innovation system.Little literatures focus on the dynamic mechanism systematically.This article proposes a dynamic model to explain the relationship between national innovation system and innovation policy system.The basic conclusion is that national innovation system plays a fundamental role when constructing innovation policy system;innovation policy system is pulling force which promotes knowledge flow in national innovation system,as to enhance the national innovation system performance.