The cathodic polarization curves of different concentrations of each component in bath were studied and the influence of rare-earth on the content of elements in composites was analyzed.Tafel curves of different coatings were tested in NaCl solution to elaborate the corrosion resistance. The optimum process criterion is obtained, which is SnCl2 20g/L, ZnCl2 40g/L, NH4Cl 80g/L, C6H5Na3O7 35g/L, brightener 15mL/L, auxiliary brightener 16mL/L, LaCl3 12g/L, CeO2 nano-particles 30g/L. It is proved that the addition of rare-earth will hinder the codeposition of Zn and Sn. Composites prepared under such circumstances obtained superior properties and good corrosion resistance.