By building a model of a typical exhaust muffler structure, a grid mesh was formed based on the calculation characteristic of the flow field. The software ANSYS CFX then was used to numerically simulate the flow and temperature fields in a muffler. The effects of the gas velocity and temperature variation on sound elimination performance, including the acoustics and aerodynamics performance, were analyzed. The result suggests that highvelocity turbulence and highspeed flow should be eliminated from muffler structures when designed. At the same time, to provide satisfactory noise elimination, pressure loss should be reduced as far as possible. The pressure loss can be decreased when reducing the perforation structure.