Abstract: In this paper, the sound transmission process and principle are briefly introduced; then, the accuracy of the established finite element TB model is verified by performing the TB modal tests, and the accuracy of the established finite element acoustic cavity model is verified by the noise transfer function(NTF) tests. In view of the roar sound phenomenon in the vehicle, the benchmarking research is conducted through the origin dynamic stiffness analysis, modal analysis, panel participation analysis and the ODS analysis; and then the relevant feasibility optimization scheme is also put forward. The results show that the main reason for the phenomenon of roar sound inside the car is insufficient rigidity of the inner plate of the car door, resulting in the modal coupling with the acoustic cavity; then the relevant feasibility scheme is provided. The optimized model can effectively reduce the peak value of NTF curve 4db to reach the target value. The results of this study provide an efficient optimization design method for solving the NTF problem.