Abstract: In order to analysis the pressure fluctuation of unsteady flow in the deep-well centrifugal pump, the unsteady flow field of a deep-well centrifugal pump was simulated with FLUENT software based on sliding mesh, the standard k-ε turbulence model, and the SIMPLEC arithmetic to investigate the pressure fluctuation of different locations. With the Fast Fourier Transform (FFT) analysis, the pressure fluctuation and frequency fluctuation are analyzed under rated flow conditions. The numerical results show that the grids number has obvious effect on the numerical results, and the pressure fluctuates generated between the impeller outlet and the diffuser inlet. The pressure pulsation period associated with the number of impeller blades, and blade passage frequency is the main factor of pressure fluctuation. The results can provide a basis to improve the pump body structure and further improve the pump working reliability.