This paper theoretically discusses and empirically examines the functional mechanisms of competitive ties and cooperative ties on knowledge transfer efficiency, their heterogeneities, and their contingencies upon institutional support as well. The hierarchical regression analysis, based on survey data from 404 Chinese firms, indicates that: both competitive ties and cooperative ties have positive effects on knowledge transfer efficiency, with no significant differences. Besides, legal support strengthens the positive relationship between competitive ties and knowledge transfer efficiency, but weakens the positive relationship between cooperative ties and knowledge transfer efficiency; and political ties positively moderate the positive relationship between cooperative ties and knowledge transfer efficiency.