The social media has become one of the indispensable work tools for government(public sector),and there are many studies on the impact of social media on government(public sector).However,we have very limited knowledge of how using social media for work purposes affects civil servants.Based on the self-determination theory,this paper analyzes the relationship between the use of social media for work purposes among civil servants’need satisfaction and intrinsic work motivation by taking Shanghai’s civil servants as an example.The research result shows that civil servants’use of social media for work purposes is positively related to need satisfaction(competence,relatedness and autonomy),and positively correlated to intrinsic work motivation.However,further analysis indicates that the excessive use of social media has a negative impact,civil servants’use of social media for work purposes has an inverted U-shaped relationship with need satisfaction and intrinsic work motivation,and different types of social media have the same effect(but different marginal effect).This paper is an innovative attempt to combine e-government and self-determination theory.It provides a certain theoretical reference for government(public sector)managers to manage civil servants’effective use of social media.