The traditional knowledge sharing theories could not be applied to the virtual team research directly. In order to overcome the barriers to knowledge sharing in virtual teams, this article extends the meta-memory directory by adding up the meta-knowledge and the social network relations dimensions to solve the problems of unifying the knowledge representation, formalizing expertise knowledge, describing the knowledge resources and exhibiting the real communication network. Centering on the meta-memory directory extension, this article formulates the model of virtual team knowledge sharing based on the interactive memory system theory, analyzes the factors in the models and develops a structural equation model for the future research.