In order to accurately evaluate the noise reduction ability of commercial vehicle aftertreatment system and meet the increasingly strict control of vehicle noise, the acoustic equivalent model of carrier and particulate filter in the aftertreatment were summarized and deduced based on the important parameter of flow resistance. The carrier was simulated by the method of complex sound velocity and complex density, and the particulate filter was simulated by the Delany Bazley Miki model under the equivalent flow resistance. Compared with the pure air property, the carrier could greatly improve the noise reduction ability above 150 Hz. The transmission loss curve was simulated using Simcenter 3D Software and compared with the data measured by the impedance tube equipment. The data were basically consistent within 1 200 Hz, indicating that the equivalent method could be effectively applied to engineering practice, and is of great significance to shorten the vehicle development cycle and improve customer experience.