With the development of policy scientification, knowledge broker has been paid more and more attention in practice and research. However, the reflection on the theoretical level of knowledge broker have not been deeply explained. Based on this, from the perspective of social network theory, this paper discusses the three "structural hole" attributes of knowledge broker, namely manipulativeness, centrality and feedback, and then constructs the structuralist theoretical framework of "integration-transport-feedback". However, while the structural attribute gives the action advantage to knowledge broker, it also contains three major tensions. The root cause of the tension lies in the separation of the tripartite structure of academic-mediation-politics in the traditional knowledge production mode. Therefore, the fundamental way to relieve the internal tensions lies in promoting the transformation from the conventional knowledge production mode with objectivism as presupposition to the knowledge " co-production" mode with constructivism as presupposition and reshaping the role and function of knowledge broker.