Knowledge management is a very popular management topic. No one doubts that bettter management of knowledge within the organization will lead to improved innovation and competitive advantage. Individuals, groups and businesses all allocate resources in the utilization of knowledge management and innovation. Yet, public orgizations seem to be less active in the practice of professional knowledge management and the information exchange of cross-boundaries activities. Employees' personal connections can be as valuable as their individual knowledge base. Social network helps maximize a company's collective smarts. In this study, I try to use the perspective of social network to explain and analyze the application of knowledge management in the public sector. I will focus on the concept and practice of tacit knowledge exchage and share. Finally, I will describe the strategies in realizing personal knowledge mangement in the public sector. Keywords: knowledge management, knowledge economy, social network, knowledge network