This chapter reports the influence of gradient structure volume fraction on the tensile mechanical behaviors of pure copper processed by surface mechanical attrition treatment at cryogenic temperature. Recently, gradient structures (GS) have been introduced into some metals and produced excellent strength and ductility. GS in materials exhibits a macroscopic gradual change in microstructure from surface to a depth. Gradient structures have been evolved over millions of years in nature and contributed to biological optimization against severe natural environments. However, the investigation of the relationship between microstructures and mechanical properties, from the atomic to the macro level and their interactions, hasn’t garnered scientific attention until quite recently. A gradient structure is generated at top most surfaces in the pure copper by CT-SMAT process, and can be optimized to produce a superior combination of tensile strength and ductility. There exists an optimum gradient structure volume fraction for the highest extra strain hardening and extra strengthening.