Abstract: In this paper, the effects of grazing flow and different perforation angles on the acoustic performance of resonance muffler are studied by numerical methods. By solving the three-dimensional unsteady, turbulent and incompressible linear Navier-Stokes equations, the influencing rule of Mach number of grazing flow on muffler transfer loss at different perforation angles is obtained. The results show that the muffler with smaller perforation angle has less resonance frequency offset at the corresponding Mach number. When the Mach number increases from 0.05 to 0.1, the resonance frequency offsets of the original muffler model and the models with perforation angles of 45°, 60°, 75° in the same direction and 45° in the opposite direction are 12.3%, 9.2%, 12.3%, 20.0% and 7.5%, respectively. At the same time, the muffler perforated in the same direction has large noise attenuation than the original model at the resonance frequency, which shows that in the flow state, the perforation angle significantly affects the muffler's noise attenuation performance, and the effect of the flow on the muffler can be effectively reduced by the perforation in the same direction.