Abstract: A cellular polyphenal composite was picked out as a new thermal-insulation roofing that shall be placed in site after a series of investigations including such factors as choice of raw materials, work process, techno-economical assessment, environment friendly requirement and energy saving. The new roofing process can combine the thermal insulation together with sloping layer even combine the insulation, leveling layer, sloping layer with air gapping layer, thus not only simplifying the roof construction and work process but making the roof better at thermal insulation properties with reasonable cost. The commercial applications revealed that the new processing could save about half of the cost.