Based on compute analysis engineering (CAE), the performances of acoustic and fluent for muffler comprehensively were analyzed and optimized in the paper. First, aiming at the heavy exhaust noise of diesel engine, bench experiments of measuring independently were designed and carried out, the frequency spectrum of exhaust noise was achieved, combining with simulation analysis of the finite element, acoustic and fluid performances of the original muffler and respective muffling cavities were analyzed, whose shortage such as transmission loss, pressure loss and flow regeneration noise were achieved, the muffler would be re-designed by CAE. Simulation shows the performances of improved mufflers were better than the original one. Eventually, insertion loss of experiment for new muffler is more 10dB(A) above than the original one, and power loss met requirement.