Based on RANS equations,the wall effect and scale effect of ventilated supercavity has been simulated using inhomogeneous model and SST turbulence model with consideration of gas-water interaction and gravity effect.The influence of different turbulence models to gas ventilation coefficient has been investigated.The developing process of ventilated supercavity under different ventilation rates is shown through numerical simulation,and the cavity shape and resistance differences at different scale and in unbounded flow field are compared.The results show that the cavity length and diameter of the small-scale model are greater than that of the large-scale model.But the extent of the upper cavity drift of the small-scale model is less than that of the large-scale model.The length,diameter and the extent of the upper cavity drift at the unbounded flow field are greater than that of in the wall effect condition.In the drag-reducing,the maximum drag reduction of the small-scale model is greater than that of the large-scale model.The maximum drag reduction of the unbounded flow field is smaller than that of in the wall effect condition.