Abstract: Hydraulic cavitation has been widely used in many fields, such as industrial production and medical care. In this paper, the effect of inlet pressure on the cavitation performance of a new type of rotor-radial groove hydrodynamic cavitation reactor is studied. By numerical simulation, the changes of cavitation volume and cavitation characteristics in rotor and stator domains were calculated under inlet pressure of 0 atm, 0.5 atm and 1 atm respectively. The results show that the cavitation strength of the reactor decreases gradually with the increase of inlet pressure. When the inlet pressure increased from 0 atm to 0.5 atm and 1 atm, the cavitation volume decreased by 33.3% and 49.6%, respectively. This phenomenon is attributed to an increase in pressure inside the fluid, resulting in an increase in the required pressure drop. The area reaching the critical value of cavitation at the suction surface of the rotor is reduced, and the cavitation intensity is reduced. In addition, with the increase of inlet pressure, the flow velocity in the main flow zone decreases, the shear effect on the fluid between the stator blind hole and the blade is weakened, the flow field in the blind hole is less affected, and the low pressure area is reduced, resulting in the weakening of shear cavitation strength.