Experimental and numerical studies are performed to evaluate and analyze the influence of the notchback rear diffuser angle on aerodynamic drag and wake structure. The relationship between aerodynamic drag and rear diffuser angle is summarized, and the flow mechanism are analyzed and discussed. A speculation regarding lower trailing vortices is proposed, and is verified in the present research model. Rear diffuser angle is an important factor influencing the wake structure, and optimizing the vehicle rear diffuser at a favorable angle can contribute to reduce the drag force and improve the wake structure.