The effects of applied normal stress, surface roughness, and initial grain size on the microstructure of pure Cu developed during platen friction sliding deformation(PFSD) processing were investigated. In each case, the deformation microstructure was characterized and the hardness of the treated surface layer was measured to evaluate its strength. The results indicated that the thickness of the deformed layer and the hardness at any depth increased with increasing normal stress. A smaller steel platen surface roughness resulted in less microstructural refinement, whereas the microstructural refinement was enhanced by decreasing the surface roughness of the Cu sample. In the case of a very large initial grain size(d > 10 mm), a sharper transition from fine-grain microstructure to undeformed material was obtained in the treated surface layer after PFSD processing. The effects of applied normal stress, surface roughness, and initial grain size on the microstructure of pure Cu developed during platen friction sliding deformation (PFSD) processing were investigated. was measured to evaluate its strength. The results indicated that the thickness of the deformed layer and the hardness at any depth increased with increasing normal stress. A smaller steel platen surface resulted in less microstructural refinement, while the microstructural refinement was enhanced by decreasing the surface roughness of the Cu sample. In the case of a very large initial grain size (d> 10 mm), a sharper transition from fine-grain microstructure to undeformed material was obtained in the treated surface layer after PFSD processing.