The object is based on 150S-50 double suction centrifugal pump. At first establish the objective function which is based on the smallest hydraulic losses using the loss extremum method, and build constraint relationship between the parameters of impeller using geometry relationship. In order to get the geometric parameters, it is important to go for optimal calculation for the function using the software called matlab which is based on genetic algorithm. At last modeling, solving the internal flow field and comparing with the previous performance. The result shows that the pump hydraulic efficiency has increased by 0.7% under the normal conditions.