Abstract: Since the different selection of control sections may cause disparity in mountain torrent disaster discharge corresponding to the disaster water level calculated by Manning formula, so the method of adjusting level-discharge relation by hydraulic radius is proposed. The method used wetted perimeter of several control sections to adjust the cross-sectional areas and discharges through the average of the hydraulic radii. The adjusted average or maximum discharge at each section is used as the result. The mean discharge is calculated by energy method and compared with the adjusted discharge. Taking the reaches of Qiaobian River in Qiaobian town and Songmen Brook in Shangfengjian village in Yichang, Hubei Province as example, the adjusted discharges are 739.1 m3/s and 94.6 m3/s respectively, which are closed to 877.3 m³/s and 101.1 m³/s calculated by the energy method. The results show that the adjusted discharge based on the hydraulic radius is reasonable.