The transient exterior flow field of a car was computed by LES, and then sunroof buffeting noise characteristic was predicted using FW-H acoustic model based on Lighthil-Curle acoustic analogy theory. Based on the study of the vehicle’s sunroof buffeting noise character, this paper introduces modern optimization algorithm to the sunroof deflector’s design. The main objective of this study is to minimize the weight sound pressure level (SPL) value of driver’s left ear and passenger’s right ear. The deflector’s installation angle、groove width and depth were taken as design variables. Based on twenty sampling points by the method of the Design of Experiment (DOE), the Kriging model was constructed. Then, the Genetic Algorithms were used to optimize the shape of the deflector, and a set of optimal parameters was obtained. Simulation results show that the monitor’s SPL of buffeting noise after the optimization of deflector reduces by up to 21.6% compared with that of the original deflector.