The performance of centrifugal pump have an important influence on the stability and efficient of flotation process in equipment of flotation. In order to catch the variation of flow field inside of centrifugal pump, the sliding mesh technology in fluent software is used to numerically simulate the flow in centrifugal pump, and then analyze the flow variation inside of centrifugal pump with vane rotating, and obtain the total pressure graphs, velocity-vector graphs and turbulent kinetic energy graphs. Thus lays the foundation for the design and the structure optimization of centrifugal pump.