Abstract: The coupling of oxy-biomass combustion and oxygen-enriched combustion technology makes it possible to realize CO_2 negative emissions. However,compared with conventional fossil fuels,biomass contains a large number of alkali metal compounds,which may aggravate the hot corrosion of the heating surfaces in combusting process,and bring great potential danger to boiler operation. As one of the key compounds in biomass ash,it is of great significance to study the corrosion behavior of KCl molten salt on heating surface. In this paper,the molten salt corrosion test of KCl was studied in the simulated flue gas high temperature corrosion test system. Two kinds of superheater and reheater materials (TP347H,HR3C) were studied in different gas environment. Meanwhile,a new salt plating system was used to simulate the condensation process of alkali metal on the tube wall. Then,the corrosion weight gain test was carried out in different simulated flue gas environment. Finally,the corrosion product on the microstructure and composition analysis were further studied. The results show that the weight curves of molten salt corrosion and atmospheric corrosion follow parabola law with time. When KCl is deposited on the surface of superheater and reheater under the same corrosion temperature,the corrosion rate is significantly higher than that of atmospheric corrosion. The increase of temperature can significantly aggravate the corrosion of the materials mentioned above. Compared with 450 ℃,the average corrosion rate of the two materials at 650 ℃ is increased by more than 16 times. Compared with the conventional air combustion mode,CO_2 can promote the migration of Cr element to the metal surface under the oxygen enriched combustion mode,thus protecting the metal surface and reducing the corrosion degree under the oxygen enriched combustion mode. The high concentration of moisture can slightly inhibit the hot corrosion. Compared with TP347H,HR3C is more resistant to molten salt corrosion because of high Cr and Ni content.