With the development of computational fluid dynamics （CFD） technology， the hybrid Reynolds averaged Navier-Stokes （RANS）/large eddy simulation （RANS/LES） method has been increasingly applied to the simulation of large separation flows and aeroacoustics in the aviation field， and fine results have been achieved. In this paper， the M219 wind tunnel model is selected to validate the hybrid RANS/ LES method under the condition of Ma=0.85， and the grid sensitivity analysis is carried out. Then， several key factors affecting the cavity flow are simulated， and the main results are obtained. Finally， the flow characteristics of tandem cavities with L/D=3.5 derived from a cavity with L/D=7 through inserting a plate in the middle are studied.