Abstract: The authors take a medium specific speed centrifugal pump with twisted blades as research object, and using given parameters, draw the axial projection figure of the impeller、spiral case section figure and spiral case plane figure.Then the components are modeled in three dimension by using software UG NX6.0.The 3D fluid zone model in parosolid form, which is exported by software UG, is imported to ICEM CFD, and meshed by grid tool CFX.ANSYS CFX12.1 is adopted to simulate the internal flow field and forecast the performance of the centrifugal pump.As a result, the centrifugal pump's extra characters such as head, shaft power etc in design conditions and several typical off-design conditions are obtained.At last, the flow rate-head figure, flow rate-efficiency figure are drawn by software OriginPro 8.The results indicate that the pump's head decreases as the flow rate increases, efficiency increases first and then decreases.The study provides important reference to designers.