The invention relates to a vacuum cylinder which can be used to produce the thermal plastic foam sheet as polyethylene, polyphenylacetylene, etc, wherein it comprises: a vacuum cylinder, a transmit band, a support column, and a water groove; said vacyym cylinder contains transmit band, while its lower part has support column; said cylinder is inclined mounted on the support column, while its upper part has vacuum exhaust open through to the vacuum pump; the lower part of cylinder has a water groove with water baffle plate; the high end of cylinder has vacuum sealing plate; and the high part of vacuum cylinder ahs the foaming sheet inlet, while its lower part has the foaming sheet outlet; the difference between the high and lower parts is 2-10m; and the diameter of said vacuum cylinder is 1-4m. |