Structured grids are widely applied due to its lower memory consuming and its convenient grid numbering. In this paper, based on the feature of geometry and fluid field, multi-block grid technique was used to generate the complicated fluid channels mesh in the centrifugal pump, and based on Reynolds equations closed by k-ε turbulence model with general coordinates, the numerical simulation of three dimensional turbulent flow through a centrifugal pump including a impeller and a volute casing in the turns of one after another was conducted by using the pressure correction algorithm. At the same time, a frozen rotor method was set between the impeller and the volute casing to transform the coupling information of flow fields. The analyses under designed operating conditions were made. Based on the calculated results of flow fields, the flow field structures in the centrifugal pump impeller and the interaction inflow between the impeller and the volute casing were obtained. And characteristics of swirling flow and its developing process on the cross-sections of the volute casing were also gained. It can be concluded that the results are very important and available for verifying the hydraulic design or the optimization design of the centrifugal pump in the engineering design field.