A combined calculation for turbulent flow and structure response of impeller was first established using two-way coupling method to study the effect of FSI of impeller on flow field in centrifugal pump. For the calculation, the flow field is based on Reynolds-averaging N-S equations and standard two equation k-ε turbulent model with the multiple reference frame, and the structure response is based on elastic structural dynamic equation. Mesh deformation, the velocity and static pressure distributions and the radial trust were analyzed, comparing with the calculated results without FSI. The analysis results indicate that, a small mesh deformation occurs in fluid and structure domain which leads to not only different distribution of load that is imposed from flow field to structure but also different impact that is made on fluid by structure, resultingly changing the distribution of flow field; the variations of static pressure distribution are different around impeller outlet and volute flow channel, according to the position of the blade relative to the cut-water; the variations of velocity distribution mostly happen around blades and impeller outlet; the magnitude and direction of radial trust have significant changes. 