In order to evaluate the M219 cavity noise at 0.6, 0.85 and 1.35 Mach number, nonlinear acoustic solver is combined with Reynolds-averaged Navier-Stokes equations. The flow field of a cavity is calculated by means of Reynolds-averaged Navier-Stokes equations, which contains basic characteristics of average flow field and turbulence statistical average solution of statistics description of turbulence fluctuation. Noise source is refactored by the nonlinear acoustic solver. Spread of pressure fluctuation is simulated precisely. A comparison shows that the simulation results of nonlinear acoustic solver agree well with the experiment results. Compared with detached eddy simulation，nonlinear acoustic solver can greatly reduce the amount of mesh. In addition, the method can provide some reference for internal weapons bay design. 