If the small amount of water in plastic raw material is not eliminated, bubble or water wave will form on the product surface and they will have a deadly effect on product strength or appearance. However, some problems lie in the traditional process of applying electrothermal drying machine to eliminating water , such as extension of product processing time (it takes one drying equipment about 15 hours to dry one-ton raw material), loss of raw material weight, high consumption of electricity, increase of production cost, ect.