This article uses a combination of k−Ω SST DDES turbulence model and SEA method to optimize wind noise simulation for a passenger car. The simulation results were improved and verified with acoustic buck wind tunnel test results, thus greatly improved the accuracy of our wind noise simulation of the level of wind noise inside the car. This improved method was also used to study the structural dimension parameters of the frameless rearview mirror and verified through wind tunnel testing. The results showed that after optimizing the rotation shaft structure, the articulation index at driver’s position was increased by 1.4%, and the sound pressure level from 2000 to 10000 Hz was significantly improved, with a maximum improvement of 5.2 dB (A). We also found that, increasing the distance between the rearview mirror and the vehicle body can effectively offset the negative impact on wind noise due to mirror’s negative open-angle. Therefore, the method proposed in this article can be an effective tool in exterior optimization for wind noise performance during the styling stage of the new vehicle program.