The social relation has an important impact on knowledge transfer. Firstly, the main research line in the knowledge management field and the research position of knowledge transfer based on social relation in the field are looked back. Then the research on knowledge transfer based on social relation is generalized into two forms, namely, knowledge transfer in view of dyadic ralation level and knowledge transfer in view of social network. Further, the main viewpoints and research lines in these two forms of knowledge transfer are concluded. Finally, the possible research directions in this field are discussed.