To improve the fuel economy of vehicles，simulation and experiments are combined to improve the aerodynamic drag coefficient during driving，taking a certain SUV model as the research object. Firstly，wind tunnel tests are used to determine the areas or components that have significant impact on the overall aerodynamic drag of the vehicle. Secondly，optimizations are made to the components or areas with high contribution values to the air resistance coefficient. The results show that the front wheel deflectors，taillights and spoilers contribute greatly to the overall air resistance coefficient of the vehicle. The restyling of the front wheel deflectors effectively reduces the frontal pressure area and interference drag from the wheels. Optimizations on taillights and spoilers improve the rear negative pressure zone and shorten the reattachment distance of separated flows on the upper part of the rear window. Based on the intrinsic orthogonal decomposition method for extracting and analyzing local flow field information，it can be concluded that the first and second order modals mainly constitute the key flow states in the wake. Compared to the initial scheme，a drag reduction rate of 7.5% can be achieved by the optimized combination design，which is verified by tests and simulations. Theoretical basis and technical support are provided in this paper for restyling and model change of the next generation of SUV.