Abstract: To solve the shortages of flow field calculation based on one dimension flow theory, a computer code was developed in Fortran language to calculate the internal flow field in centrifugal pump impellers based on continuity equation and motion equation. The iterative calculation was conducted by applying the finite-element method on the S1 stream surface and the streamline-curvature method on the S2 stream surface. The distributions of pressure and velocity in the impeller were obtained from the numerical calculation as the iteration converged. Results showed that the relative velocity distribution in the impeller was reasonable. The velocities at the blade head between pressure surface and suction surface were different due to the impact action of the fluid on blade head. The pressure in impeller increased gradually from impeller import to export and the pressure gradient was small. The pressure at the impeller inlet decreased from hub to shroud. Compared to the results of the traditional method, the meridional velocity distributions of this method based on both fluid continuity and motion equations were obviously different in each stream line from hub to shroud, with the maximum difference in the impeller inlet. The three-dimensional characteristic of the velocity distribution is distinct, which demonstrates that the numerical results of this method can reflect the three dimensional flow law more accurately.