An evaluation function of muffler was defined to describe the weighted insert loss, exhaust back pressure coefficient and linearity coefficient in a comprehensive quantitative way, so as to analyze sound reduction effect, aerodynamic performance, as well as sound quality characteristics of the muffler in multiple working conditions. The evaluating functions of three different mufflers were computed by simulation with GT-Power and experiment tests. The comparison shows that the evaluation method could describe the comprehensive property of a muffler under multiple conditions, which could be used in muffler's matching design.