The internal flow in impeller and volute of QW950—15—55 double-channel passage pump was investigated. Based on the Reynolds-averaging N—S equations and standard k—ε two-equation turbulent model, the simulations of turbulent flow between impellers are performed by using the flow computing software Fluent under different operating conditions. Important flow features were obtained. With the computing result, the distribution of velocity and pressure in the impeller was analyzed. The pressure and velocity distribution in impeller are similar to those in general centrifugal pump. Obvious asymmetry of flow field was observed in impeller in case of large flow operating condition. The internal flow in impeller is mixed spiral flow and the vortex core resulted by relative eddy is close to the back blind flange and pressured side. The circumferential distribution of pressure and absolute velocity at the outlet of impeller is periodic, which is corresponding to the periodicity of the passages of impeller. The asymmetry of pressure is relatively weak but that of velocity is strong. Comparing the data of efficiency with the head produced by experiment and CFD, the result mainly tallies. 