Abstract: Few scholars touch on the impact of leadership style to knowledge integration. The definition of knowledge integration proposed by Nahapiet and Ghoshal is developed into knowledge donation and knowledge combination. Then, a empirical analysis is carried out to explore the mechanism of transformational leadership to knowledge integration, which is mediated by employee trust. The results show that transformational leadership has a significantly positive effect on knowledge integration and employee trust; employee trust plays a partial mediative role between transformational leadership and knowledge integration; employee trust is remarkably positive related with both knowledge donation and knowledge combiniation; employee trust and knowledge combination is partially mediated by knowledge donation. Through a data analysis, it is also found that transformational leadership and employee trust have greater explanation degree on knowledge donating than that of knowledge combining.