Abstract: Flow regime in the mountain river is characterized by its complex boundary topography,fluctuating water level and rapid flow velocity.A two-dimensional horizontal numerical model,which is solved by the mixed five-diagonal finite difference algorithm,is developed for modeling water level and flow velocity in the mountain river.This model is verified by the topographic and depth-averaged flow velocity data from the Jingangbei-Chaoyangqiao section near Chongqing in the Jialingjiang River.Good agreements are found in comparison with the measured water level and flow velocity.