XPS foamed sheet, also named Polystyrene Extrusion Plastic Sheet (XPS for short) has a perfect closed-pore alleviate structure. Its density, water absorption, coefficient of heat conducting and the coefficient of steam pervasion are all lower than those of other sheet heat insulating materials and they have the characteristics of strong intensity, light material, airtight, anticorrosion, ageing resistance, low cost, etc. It has been widely used in the fields of heat preservation in the construction industry and the highway, railway, airport, square of the heat preservation and household fitment. It is the generally acknowledged and the best heat insulator in the market at present.