The sulfidization mechanism of S-2 on the massicot surface was simulated by density function theory (DFT) calculation to illustrate the microscopic reaction mechanism during the surface sulfidization process of lead oxide minerals at high temperature. The calculated results showed that the massicot (1 0 0) surface was the most stable cleavage surface and the main active sites were the O atoms of the surface. The S atoms more easily absorbed on the O atoms of massicot surface in contrast with Pb atoms, leading to the formation of sulfur dioxide in the following reactions. The density of state (DOS) results revealed that O 2p orbital at surface layers of the massicot and S 3p orbital of S-2 overlapped ranging from -0.7 to 0.7 eV, implying that chemical adsorption could occur. The results of Mulliken population suggested that the oxidation and reduction reactions of S atoms from the sulfidization agent were simultaneously involved in the adsorption process. This paper revealed the mechanism of surface sulfidization at an atomic level. It was expected that the study could provide a theoretical reference to improve the sulfidization roasting performance of massicot.