Abstract: Based on the kinematic equation describing transient flow in a river,a numerical calculation method is developed to simulate the propagating process of the transient flood wave and dam-break wave in a natural river and on dry river beds.By use of this method,the transient flood process of Xiangjiaba Hydropower Station in Jinshajiang River is simulated,and influences of the transient flow on ship sailing and harbor operation 165 km downstream of the dam are analyzed.