Abstract: The condition of amorphous formation of Ni - W electrodeposition was studied , and the structure area of amorphous and crystalline was drawn out. A displacement solid solution made up of solvent Ni and solute W was determined by X -ray diffraction experiment. The solid solution has a f. c. c structure. The formation of amorphous deposit was explained by calculating the change of lattice constant, crystal grain size and its change with the change of structure. Furthermore, the corrosion rate of amorphous deposit in acid medium was tested. The chemical formula of passivated film was Ni(OH)2·WO3·nH2O by XPS analysis.