The invention belongs to the technical field of metal stamping part machining, and particularly relates to a machining method of automobile covering part surface hardening. The machining method comprises the steps of pretreating an automobile covering part, treating the automobile covering part through a treating agent and coating the automobile covering part with a coating. Compared with the prior art, the machining method has the following beneficial effects that after being cleaned, the surface of the automobile covering part is treated through treating liquid and coated with the coating, the surface hardening effect of the automobile covering part is good, the combination degree of a thin film on the surface of the automobile covering part and a matrix is high, high cohesiveness and weather fastness are achieved, and the wear resistance and impact resistance of the surface of the automobile covering part are greatly improved; and tall oil fatty acid, graphite scale and other raw materials are used in cooperation, and therefore the smoothness of the matrix of the automobile covering part can be effectively prolonged, the service life of the matrix of the automobile covering part can be prolonged, subsequent maintenance and repairing on the automobile covering part can be reduced, and the maintenance cost can be reduced.