The invention discloses a simulation calculation method for an aerodynamic performance of an automobile wind protecting cover. The simulation calculation method for the aerodynamic performance of the automobile wind protecting cover comprises a first step of building a physical model of the fan wind protecting cover; a second step of carrying out calculation region setting and grid division; a third step of setting border conditions; a fourth step of carrying out simulation calculation on the aerodynamic performance of the wind protecting cover in the presence of a given rotating speed of the fan by utilizing CFD simulation software Fluent; and a fifth step of optimizing a wind protecting ring structure based on a vortex dynamic theory and characteristics of a flow field around vanes, and benchmarking with experimental data to verify accuracy of the model. By post-processing a simulation calculation result and utilizing the vortex dynamic theory and the characteristics of flow lines around the fan, the structure of the wind protecting cover is optimized, and the performance of the fan wind protecting cover is accordingly improved.