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Electroforming nickel was prepared from a purified sulfamate system. The effects of cathode-current density, temperature and pH of the solution on the microstructure, internal stress and mechanical properties (tensile strength and elongation) of electroforming nickel layer were investigated by metallographic microscope, cathode bending method and tensile test. The results show that the properties of electroforming nickel layer are influenced by microstructure, while the microstructure is influenced by electroforming parameters; the grain size of electroforming nickel decreases with the decrease of cathode-current density or the increase of temperature; when the pH is 4.0, the grain diminishes too; with the decrease of the grain size, the tensile strength of electroforming nickel layer increases while internal stress and elongation decrease. By optimizing technology parameters, the electroforming nickel layer with excellent properties are prepared, including the tensile strength of 673 MPa, elongation of 23.2% and internal stress of 48 MPa.