Abstract: The frost formation of cryogenic encloser is studied with simulation method. A mathematical model is established by energy conservation and mass conservation during frosting process, in which heat transmission and mass transport process are considered. Then the influence of inflow air temperature, relative humidity, flow speed and cold wall temperature on the surface temperature and thickness of frost layer are analyzed based on the model. The simulation shows that the influence of inflow air and cold wall temperature are larger than those of flow speed and relative humidity. The necessity is pointed out to adopt some heat insulation and frost protection methods during cryogenic liquid filling process.