The invention relates to the technical field of metal strengthening, in particular to a method for improving the mechanical surface strengthening effect. According to the method, before mechanical surface strengthening treatment is conducted, a certain surface structure is machined on the surface of a treated metal material. The method for improving the mechanical surface strengthening effect includes the steps that the surface structure is machined before mechanical surface strengthening treatment is conducted, a larger and deeper residual compressive stress layer can be generated on the treated surface through mechanical surface strengthening treatment; residual compressive stress with preset directivity can be generated on the treated surface through mechanical surface strengthening treatment; the residual compressive stress value of the topmost surface is increased, so that the mechanical surface strengthening effect is further enhanced; and the treated surface layer is more likely to generate severe plastic deformation and grain refinement, and an ultra-fine grain or a nanocrystal surface layer material is prepared conveniently.