Abstract: One of the critical problems in metallic materials is how to enhance their strength while keeping their conductivity. The prevalent strengthening methods employed usually lead to a pronounced decrease in conductivity. In this study, high-purity Cu foil samples with high density nanometer sized twins were synthesized by means of a pulsed electro-deposition technique. For Cu samples with an average twin lamellar thickness of 15 nm, the tensile yield strength could be as high as 900 MPa, and the ultimate tensile strength was 1068 Mpa, which is about 10 times higher than that of coarse grained Cu. The most interesting phenomenon is that this sample also retains a very high conductivity comparable to that of pure Cu.