Solid-state shear milling (S3M) equipment, developed based on the principles of solid-state mechanochemistry, employs a unique three-dimensional shear field, enabling the ultrafine pulverization and micro-nano dispersion of polymer materials at room temperature. It is thus a crucial technology for waste plastic recycling. To enhance the grinding efficiency of the S3M equipment, this paper further optimized its structural design by incorporating pile-tooth structures on the inclined surfaces of the grinding teeth. Computational fluid dynamics (CFD) simulations, performed using Flow Simulation software, were employed to evaluate the resulting dynamic shear-stress field. The results demonstrate that key structural parameters, including the geometry, height, and distribution density of the pile tooth, significantly influence the generated maximum equivalent shear stress. Under the optimized configuration (the quadrangular prism pile tooth with a height of 0.3 mm, and an inter-pillar spacing of 5 mm within each column), the maximum equivalent shear stress reaches 29.3 MPa. These values correspond to increases of 350% over those generated by a conventional disc design without pile tooth.