For cascade hydropower stations in the medium or small river, tributary flow may account for a large proportion of total runoff.It is necessary to consider the high efficiency utilization of tributary flow when deciding short-term operation of cascade hydropower station. Taking the cascade hydropower stations on Shouduogang river for example,the paper proposed a short-term optimal operation strategy considering the influence of tributary inflow. It is necessary to take the position of tributary flow as boundary so as to make cascade hydropower stations become a multiple sub-cascade. Meanwhile,output level of the downstream sub-cascade should also be determined based on tributary inflow and local inflow,installed capacity and characteristics of generation electricity of the hydropower stations. Then, the load demand distribution solutions and water replenishment amount of uppermost reservoir can be obtained.The utilization efficiency and aim of storage of hydropower of cascade waterpower can be improved with less abandoned water. The strategy proposed by the paper is reasonable.