In this study, three impellers with different blade pressure side (PS) profiles are designed and the influence on the hydraulic and dynamic performance of a low specific speed centrifugal pump is investigated by numerical simulation and experimental research. The results show that blade PS modification introduced in this study can efficiently alleviate the unsteady pressure pulsation of model pump. In order to study the effects of blade modification on the internal flow filed, the volute domain is replaced by an even outlet region for computational fluid dynamic (CFD) analysis. Relative velocity distribution is extracted to visualize the three-dimensional (3D) flow characteristics at the impeller outlet. Results show that the flow at impeller outlet presents a typical jet–wake structure, which is significantly suppressed after the blade modification. The suppression of jet–wake structure, which is attributed to the redistribution of pressure and velocity in the impeller caused by the change of blade work capacity, can directly reduce the intensity of pressure pulsation in the volute by increasing the velocity uniformity at impeller outlet. Given that the existence of jet–wake flow results in large mixing loss and velocity deviation at the impeller outlet, entropy generation rate and slip velocity calculation are introduced here to measure the extent of jet–wake configuration. Results show that both indicators introduced here can be used to quantify the extent of the jet–wake structure at impeller outlet, and thus, indirectly predict the strength of unsteady pressure pulsation in pump volute.