Minjiang River is a very importanttributary of Changjiang River. It is located in the eastern margin of tibetan Plateau where is a suddenly changed area for geology,geomorphology and climate. The research was initiated to further understand its incision and influences. The linear relationship between river terrace and river incision was used to determine incision rate in the middle reaches of Minjiang River . Through calculation,the authors found thatthe average incision rate in the middle reaches of Minjiang River is 1. 08 mm/a. This work furnishes a fresh basis for further study of soil erosion and crustal movement.