Abstract: A design ideal and design method for the mobile bed erosion model of a new excavated channel are presented, it shows that the method of designing the mobile bed model of the natural channel is diffferent from that of the new excavated channel due to the evident difference between the undistrurbed soil and individual sand in threshold velocity and sediment discharge, furthermore, which has been verificated to be accuracy and has a practical application value by the Tai-zhou approach channel mobile bed erosion model.