Structured grids are applied widely due to its lower memory consuming and its convenient grid numbering. It is unfavorable to describe the complicated fluid channel in the centrifugal pump impeller by mono-block grid. In this paper, based on the feature of geometry and fluid field, multi-block grid technique was used to generate the complicated fluid channel mesh in the centrifugal pump impeller, and the standard k-ε turbulence model and wall function were adopted to solve 3D turbulent flow field in the impeller of a centrifugal pump. The influences of the blade profile on speed distributions, press distributions and pump performance were analyzed. The flow regulation pattern in the impeller of a centrifugal pump was also investigated. A redesign and optimizing method of the impeller blade profile based on numerical analysis of 3D turbulent flow was put forward. The results show that accurate and abundant flow field data were provided for the impeller modification. The proposed method is a very outstanding tool to improve the level of the impeller modification.