Vibration in centrifugal pump still remains a tough problem to solve. Many studied have been done to find the relationship between hydraulic design and vibration. Both experiments and numerical simulation methods have been proposed to make clear the influence of pump parameters related to vibration. It is evident that unsteady phenomena in centrifugal pump are the main factors causing vibration. Also motor-stator interaction of impeller and volute keeps predominant role considering hydraulic factors.Till now almost all reported researches consider pump geometry parameters, but the shape of volute is rarely proposed. To reduce interaction between impeller and volute tongue, a special volute with slope diffuser section is put forward in this paper. The relative position of volute tongue changes compared to the conventional spiral volute. Thus the effect of flow field striking with volute tongue can be receded effectively, and vibration will be reduced.As the developing of computer technology, it is possible for us to achieve the unsteady flow field inner pump by using numerical simulation methods. A commercial software Fluent was adopted to analyze pressure pulsation and radial load of model pump. Slant angle and clearance rate were optimized considering pressure magnitude. It is observed that pressure amplitude at blade passing frequency achieve the lowest level at slant angle 15°. Pressure magnitude decreases significantly with the increasing of clearance, but limited to radial size of volute, it is suggested to be in the range of 0.134∼0.250.Several monitor points are selected along the volute to have overall understanding of pressure pulsation characteristics. Pressure pulsation at blade passing frequency keeps the predominant in motor-stator interaction. Amplitude of both pressure and radial load increase rapidly when pump operating at off designed conditions.Copyright © 2013 by ASME