Abstract: Molybdenum alloy is widely used in high-temperature service environments such as aerospace, nuclear power, etc. due to its high melting point, excellent electrical and thermal conductivity, and outstanding high-temperature mechanical properties. However, molybdenum alloys are prone to oxidation and failure fracture in high-temperature service environments. So that it is necessary to develop anti-oxidation coatings on the surface of molybdenum alloys. In this paper, the Mo-Si-B coatings were prepared by the molten salt method on the surface of molybdenum alloys and the effect of molten salt composition (B) on the microstructure and oxidation resistance of the coatings was explored. The results showed that when the B content in the molten salt is 0.4 mol, the composition of the molybdenum alloy surface coating is MoSi2 and the coating thickness is 12.17 μm. As the B content increased to 0.6 mol, the main component of the coating was MoB, and a silicide coating was not successfully prepared. The oxidation experiment showed that the silicide coating prepared by molten salt method showed good oxidation resistance at an oxidation temperature of 800-1200 ℃, which was mainly attributed to the formation of SiO2 glass phase on the surface of the coating.