Abstract： Effective knowledge transfer is an important approach for enterprises to win the competitive advantage. It is well known that, the informal network, for its favorable interaction and pervasion, shows the important effect on transferring tacit knowledge. Although there is much research on the influencing factors of tacit knowledge transfer, systematic research on the background of informal networks is rare. Therefore, the model for mechanism of tacit knowledge transfer and its influencing factors in the context of informal networks are proposed and tested. The model manifests that the characters of informal networks and communication are positively related to the tacit knowledge transfer and then individual willingness and frequency of communication mediated the relationship between the characters of informal networks and tacit knowledge transfer. At last, it is found that the tacit knowledge moderated the relationship between trust, job interaction, and tacit knowledge transfer.