Abstract: Carburizing, as a common heat treatment process for metal surface treatment, is used to improve the surface hardness of steel while ensuring the toughness and plasticity of its core. Several carburizing methods（solid carburizing, gas carburizing, vacuum carburizing, plasma carburizing） were summarized, and the working principle, application scope,advantages and disadvantages of each carburizing method were introduced. In order to reveal the working mechanism of carburizing, the research status and application of carbon atom diffusion were described. The research methods of carbon atom diffusion includes hardness method, micro area analysis method, electrical resistance method and the first principle calculation of carbon diffusion. The carburizing technology research in bearing steel, gear, composite plate, etc was described. Finally, the development trend of carburizing process and the future research of carbon diffusion were prospected.