Based on the Reynolds time-averaged N-S equations and standard k-ε two-equation turbulent mode, using multiple reference model and wall function method, the inner flow fields were simulated which is a part of three different kinds of impeller on stamping and welding multistage centrifugal pump by CFD software FLUENT. The characteristic of internal flow on multistage pump was analyzed base on the calculated results, so as to reveal how the flow regulation influences performance of pump. The result shows the internal flow condition in the distort-type impeller pump is more reasonable than the other two groups, there is not the flagrant whirlpool and the capability of cavitation-resistant is strong.