The unsteady full flow fields at shut off condition in a centrifugal pump with specific-speed of 86.44 were simulated by unsteady Reynolds averaged Navier-Stokes approach and SST model. The head of the pump at SOC was predicted based on CFD results. Through the comparison and analyses, it was concluded that the average head prediction errors was 4.7% compared with test result. There were two eddies in impeller flow passage No.1 and the rotation direction was opposite. The velocity at volute diffusion part was very small. The high speed area of the pressure surface in impeller flow passage No.1 increased first and then decreased. The pressure distribution in the volute changes evidently, and the high pressure area of the pressure surface in impeller flow passage No.1 at the exit area constantly decrease as the impeller rotates. There are always six different sizes of vortexes at the impeller inlet and the vortexes nearly block the whole impeller passage.