Abstract: In addition to sulfide content, the morphology and distribution of non quenched and tempered steel with high requirements need to be controlled. The high temperature deformation mechanism of sulfide in non quenched and tempered steel was studied.The results show that when the steel is heated, the sulfide in the steel begins to deform with the increase of temperature and the extension of holding time. The small sulfide gradually dissolves into the matrix, and a series of morphological changes such as extension, dissolution, fracture and spheroidization occur in the larger sulfide. After the austenitizing of the steel, the sulfide changes more obviously.When the heating temperature reaches 1200℃, the deformation becomes more active. With the extension of holding time, the fracture and fragmentation of long strip sulfide in steel accelerates and the number increases.