Effects of electrolysis conditions on the microstructure and mechanical properties of copper electro-formed layer have been investigated using the copper sulfate. Electroforming was conducted at bath temperature of 25 to 55℃ and current density of 3∼20A/d㎡ for 10 hours on silver mirror-treated silicon rubber. The microstructure of copper layer was found to be dependent upon the electrolysis condition. The microstructural observation revealed that fine grains in the copper electroformed layer were formed in low current density and at bath temperatures of 25∼35℃. The tensile strength and elongation of copper electroformed layer tended to increase with decreasing bath temperature, and the peak tensile strength showed 380 MPa at bath temperature of 25℃. The tensile strength showed the highest value of 300 MPa at 7A/d㎡ of current density, and decreased when the current density increased above 7A/ d㎡. The Ni coating, with a thickness of 20 ㎛, on the copper electroformed layer improved microhardness(Hv) significantly and tensile strength slightly because the thickness of the Ni coating is thin.