Aiming at the pressure pulsation of water pump turbines, computational fluid dynamics (CFD) was used to carry out the numerical analysis of the whole flow channel. 61 monitoring points were set up along the circumferential direction in the bladeless area between the movable guide vanes and the runners, and the pressure fluctuations in different working conditions of the hydraulic turbine working conditions and the water pump working conditions was analyzed. The relationship between the flow field and pressure pulsation under different working conditions was analyzed. The results show that the pressure in the bladeless zone of the hydraulic turbine working condition and the pump working condition presents a periodic distribution on the time and space scale. The pressure distribution of the hydraulic turbine working condition is mainly determined by the runner blades, and the pressure pulsation of the pump working condition is mainly determined by the movable guide vanes.The pressure pulsation of the pump working condition is stronger than that of the hydraulic turbine working condition.