According to the use problem of bypass perforated tube muffler, the software Fluent was used to analyze the changing rule of pressure loss of bypass perforated tube muffler unit under different inlet flow rates, perforation diameter and perforation rate. According to the analysis of simulation results, the bypass perforated tube muffler was derived for the double and triple bypass perforated tube muffler, and relation was researched of the difference of derived structure and the original structure under the same perforation diameter and perforation rate in pressure loss. And the result shows that the double bypass perforated tube muffler has a better performance than other two. By test on the muffler which contains bypass perforated tube, the result of simulation and test shows that that pressure loss is 6.1 kPa, as by simulation the result is 5.75 kPa, so the error is only 5.73%, which verifies the calculation accuracy of computer fluid dynamics (CFD) simulation.