The guide vanes were designed by using the axial flow pumps isolated blade design method based on Gottingen airfoil blade. The experimental studies on the basic rule and the regulatory mechanisms of prewhirl regulation for the centrifugal pump were made. Comparison experiment tests showed that the inlet guide vane installed with long-string side close to the center axis on the improvement of the external characteristics of centrifugal pump was better than the other. Also the inlet guide vane installed with long-string side close to the center axis has enlarged the high efficiency scope and improved the hydraulic performance of the centrifugal pump. When compared with the performance of the centrifugal pump without inlet guide vane, the peak value of efficiency was enhanced by 2.3% after the guide vane was installed. This method improved efficiency and saved energy for the centrifugal pump.