Abstract: WeChat group has become the most active community for people to socialize in mobile online network. The study of users' willingness to share knowledge in different WeChat groups from the perspective of social capital is an important issue that deserves to be explored in depth and has extensive implications. Based on social capital theory, this paper divides the WeChat group into three types: bonding group, maintained group and bridging group. It explores the influence of social capital in three dimensions of structure, relationship and cognition on the users’ willingness to share knowledge in three types of WeChat groups and their differences. WarpPLS is used to validate the model with 244 valid samples obtained from the questionnaire. The research results show that in terms of structural dimension, network connectivity only positively affect the user's willingness to share knowledge in bridging group. Network intimacy only positively influence the user’s willingness to share knowledge in maintained group and bridging group; In terms of relational dimension, identity positively influence the user’s willingness to share knowledge in bonding,maintained and bridging group,however, trust and reciprocity only positively affect the user’s willingness to share knowledge in bridging group; in terms of cognitive dimension, shared language positively affect the user’s willingness to share knowledge in bonding,maintained and bridging group,but shared vision only positively influence the user’s willingness to share knowledge in maintained group. This study has important theoretical and practical significance for individuals or organizations to understand the rules of knowledge sharing in the WeChat group representing different interpersonal circles, so as to acquire knowledge efficiently and carry out innovation management.

Key words: social capital, WeChat group, knowledge sharing willingness