Abstract: The SiO2/S composite coatings were coated by chemical vapor deposition on 25Cr35Ni alloy substrate using methyl disulfide (DMDS) and orthosilicotetraacetate (TEOS) as reactants.Thermodynamic calculation and analysis of the formation reaction of SiO2 and S and the chemical reactions among the reaction products were done by thermodynamic potential function,and the ratio of CVD source materials chosen was discussed.As shown by the experimental results,chemical vapor deposition of the SiO2/S composite coating with preheating temperature of 773 K and deposition temperature of 1 023 K under normal atmospheric pressure was feasible.