The two extruders are arrayed in a series way. It takes general polystyrene as raw material. It injects vesicant with high pressure into the barrel of first extruder in course of process. After coming out of die head, the plastic flow will go through the cooling calibrating unit before coming into shape of sheet. With the vacuum thermoforming machine, the sheet can be turned into various kinds of packing containers, such as fast-food box, instant noodle bowl. Besides, the sheets are widely used as KT board and thermal-insulate board, and so on.