Abstract: A type of small hole composite muffler is designed，basing on the analysis of the causes for the noise on field，as well as the muffling principles of reactive muffler and small-hole muffler.Introduced are the application conditions of the said muffler such as the field arrangement，the device design and the process flow.The performance of the application is also evaluated.The noise reduction cylinder is evenly covered with Φ2 mm holes and sealed up on one end.When air passes by the holes on the cylinder，its pressure and flow rate is reduced，so the jet noise will shift to high or ultrahigh frequency range and its audible frequency part will be significantly reduced.In this way the noise is reduced from 110 dB to 80 dB.