The work aims to study corrosion property of 45CT coating prepared by HOVF in KCl + K2SO4+ Na2SO4 molten salt, and understand the protection and failure mechanisms of 45CT coating in molten salt. The samples were immersed in KCl+K2SO4+Na2SO4 mixed molten salt to obtain corrosion kinetic of the samples in the molten salt at different temperatures. The composition, structure and morphology of high temperature corrosion products were investigated by using XRD, SEM and EDS. Main corrosion products of the 45CT coating corroded molten salt were identified as Cr2O3 and NaCrO2. The coating could protect the substrate effectively and the layer of corrosion products on it was thinner at 600 ℃ and 650 ℃. However, the coating degraded seriously at 700 ℃ and a lot of sulfides were detected in the coating. Fe in the substrate diffused toward the coating. Sulphidation occurs easily in 45CT coating at high temperature, leading to weak bonding between the oxide film and coating. As temperature increases, hot corrosion of 45CT coating in KCl+ K2SO4+Na2SO4 molten salt becomes more serious and results in faster coating degradation.