In order to investigate the characteristics of pressure fluctuation in cycloid rotor oil pump, based on RNG k-ε turbulence model and moving mesh, the transient flows for different operating conditions in cycloid rotor pump were investigated numerically and the computational results of flow and efficiency were obtained. The pressure fluctuation at different monitoring points were measured and analyzed in time and frequency domains. The results show that the pressure fluctuation of the flow field in the cycloid rotor oil pump is periodical obviously, the amplitude of pressure fluctuation is smaller in the oil inlet chamber and decreases gradually along the oil pipeline of the outlet, the dominant pressure fluctuation frequencies of different monitoring points are fundamental frequency and the second harmonic under corresponding working conditions, the amplitude of pressure fluctuation increases gradually with the increasing of rotational speed. The pressure pulsation test is performed on the outlet of the rotor oil pump and the results shows a good agreement with the simulation results, which verifies the reliability of simulation results.