Abstract: The existence of cavitation will lead to different intensity of vibration, shocks as well as acoustic noise and worsen the cavitation erosions which results in structural fatigue failure. In order to suppress the evolution and detachment of bubbles efficiently, based on the existing experimental phenomena, a new idea is proposed to achieve cavitation flow control by setting pits on the suction side of the hydrofoil. To study the impact of this new structure on cavitation flow field, in this paper, the unsteady cavitation flow around the NACA66 (MOD) hydrofoil at 8° angle of attack was simulated by Realizable k-ε turbulence model combined with Schnerr-Sauer cavitation model for different cavitation numbers, pits size and pits location. The results indicate that the simulated cavity shapes around foil were well fitted with the experimental high speed images, and showed that the selected models can better predict the cavitation flow. The results also showed that for the study of the non-cavitation flow, the suction side pits led to the decrease of the hydrofoil lift-to-drag ratio and impair the hydrodynamic performance. However, this was very different from that in cavitation condition. In addition, the analysis of the dynamic characteristics of the 2D hydrofoil cavitation flow field and the effect of hydrofoil surface structure factors on cavitation suppression showed that the tail position of cavitation closure region was very close to that of the pits which located at 0.32 chord (0.32c) distance from leading edge for the sheet cavitation (Cavitation number=1.23). The presence of the pits changed the direction of the re-entrant jet and caused the severe dissipation of the kinetic energy of the re-entrant jet. As a result, the re-entrant jet was blocked to enter the cavity body, and therefore, the cavitation shedding and vibration frequency decreased. However, the evolution of cavity had not been suppressed along with the increased cavity length because local low pressure region formed at the position of pits (0.32c) celebrated the development of cavitation flow. But when the pits were placed at 0.2c distance from leading edge, the maximum cavity length was shortened 3% compared with that for normal hydrofoil without any changes of lift-to-drag ratio. The structure of pits played a positive role in controlling cavitation flow when the sheet cavitation occurred. Moreover, for cloud cavitation (Cavitation number=0.81), when the pits were placed at 0.2c, the lift-to-drag ratio increased and shedding frequency decreased which showed a good hydrodynamic performance. The effect analysis of pits structure size and position on cavitation flow revealed the pits had an obvious effect of suppressing cavitation after the cavity length reach maximum. The size of the detached vapor cloud and the low pressure distribution zone of the trailing edge were significantly smaller than that of the normal hydrofoil, therefore the vortex at the trailing edge were suppressed. Through the spectrum analysis of the lift coefficients of different hydrofoils, it is found that the presence of the pits weakened the hydrofoil vibration caused by the detachment of cloud cavity. That meant that with the proper design of pits, the hydrodynamic efficiency was increased and the unsteady behavior of the cavitation could be suppressed. Finally, the study of the boundary layer velocity and pressure distribution of the hydrofoil suction side revealed that arranging the pits on the suction side of the hydrofoil could reduce the thickness of the boundary layer of the hydrofoil surface and enhance the anti-reverse pressure capability, but it accelerated the re-entrant jet near the pits. Therefore, cavitation could be suppressed only when the anti-reverse pressure gradient capability was greater than the impact of the re-entrant jet. The conclusions obtained in the numerical calculations showed that the proper suction side pits can suppress cavitation, broaden the scope of passive control technology research, and also stimulate the subsequent research of cavitation suppression methods.