Abstract: Minjiang River is a very important tributary of Changjiang River and is located in eastern margin of Tibetan Plateau which is an important constitute of geotectonic units of China. It is also a changed area of geology, geomorphology and climate. The authors according the linear relation between river terrace and river incision studied the incision rate of Minjiang River's upper and middle reaches, and reached a conclusion that the average incision rate of Minjiang River's upper reaches is 29.62% larger than the average incision rate of Minjiang River's middle reach. The reasons are the difference in the channel gradients of Minjiang River's upper reaches and middle reaches, and the elevation movement of earth crust which is different under the river channel.

Key words: a triburary of the Changjiang River, the upper and middle reaches of Minjiang River, river incision rate