Abstract: For researching the influence of impeller and blade two cutting methods at different cutting angles on the external characteristics of centrifugal pump, the flow in middle specific speed pump was simulated by using FLUENT software after impeller cut, and the external characteristics were also predicted. The existing cutting formulas were revised considering the influence of cutting angle, cutting value and specific speed. The predicted external characteristics show that the head reducing quantity after cutting impeller is significantly greater than that after cutting blade in the same cutting value. When the cutting angle is in the range of 0° to 10°, the efficiency in the forward skew cut is higher than that in the straight cut and the backward skew cut. The shaft power in the impeller cut is obviously lower than that in blade cut. When the cutting angle is in the range of -10° to 10°, the shaft power in the skew cut is lower than that in the straight cut. The results of the inner flow analysis indicate that in the same cutting value the forward skew cut significantly weakens the vortex phenomenon in the straight cut with the increase of the cutting angle. No matter the straight cut or the skew cut is conducted, the effect of blade cut is better than that of impeller cut in the same cutting value. The research results can provide reference for the impeller cut of middle specific speed centrifugal pump.