Abstract: The main feature of the sodium-cooled fast reactor (SFR) is the application of liquid sodium as the coolant. Hence, the wetting phenomenon at the solid-liquid interface between stainless steel and liquid sodium is significant in this reactor system. Solid-liquid interface wettability is one of the important factors affecting the corrosion of solid materials. The better wettability will make liquid sodium more likely to penetrate the stainless steel substrate and react with internal elements, indicating that the material’s resistance to liquid sodium corrosion performance is worse. For some moving parts, the worse wettability indicates better self-cleaning properties of the material, which can greatly reduce the cost of cleaning and maintenance. In addition, the testing of some physical instruments is also related to the wettability of the liquid sodium, which is not in full contact with the measuring parts until the instrument probe is fully wetted, which can lead to less accurate measurement data. The wettability can be quantitatively characterized by the contact angle. The wetting mechanism of liquid sodium was investigated on the surface of stainless steel flats and Cr₂O₃-coated stainless steel flats based on experimental measurements and molecular dynamics simulations in this paper. In the experimental part, stepped heating wetting was used to measure the contact angle of liquid sodium at different wetting time and temperatures, and to investigate the effect of chemical reaction between liquid sodium and Cr₂O₃ layer on the surface of stainless steel on the wetting turn and complete wetting temperature at high temperature. In the simulation part, the molecular dynamics method was used to simulate the wetting process of the liquid sodium model on two stainless steel model surfaces with or without the Cr₂O₃ layer under constant wetting conditions, to investigate the effect of the presence of Cr₂O₃ on the surface of stainless steel on the precursor film of liquid sodium as well as the equivalent wetting radius. It is found that the wetting characteristics of liquid sodium on stainless steel surfaces are mainly regulated by temperature and wetting duration. The contact angle decreases with rising temperature and longer time, leading to better wetting effect. The wetting turning temperature and complete wetting temperature of liquid sodium on stainless steel surface are in range of 320-335 ℃ and 510-530 ℃. In addition, it is also found that Cr₂O₃ on the surface of stainless steel will deteriorate the wetting effect of liquid sodium, and the contact angle increases with Cr₂O₃. The Cr₂O₃ layer will also inhibit the generation of the precursor film of liquid sodium, making the equivalent wetting radius of the liquid sodium decrease. When the liquid sodium and stainless steel surface Cr₂O₃ react at high temperatures to generate NaCrO₂, the liquid sodium wetting turning temperature and complete wetting temperature are reduced, and the wetting effect turns well.