NOVELTY - Polyvinyl chloride (PVC) composite material useful for a biogas digester, comprises emulsion-polyvinyl chloride (E-PVC) paste layers, base coat layers and high-strength polyester sandwiched fabric, where the base coat layers are formed by coating top and bottom surfaces of high-strength polyester sandwiched fabric with base coat layer coating liquid, drying, plasticizing and cooling; the E-PVC paste layers are formed by coating base coat layers on surfaces of the high-strength polyester sandwiched fabric with E-PVC paste layer coating liquid, drying, plasticizing and cooling.    USE - The PVC composite material is useful for a biogas digester.    ADVANTAGE - The PVC composite material has improved surface dryness, high physical and mechanical properties even after aging, excellent aging resistance, scraping resistance, and oil resistance.    DETAILED DESCRIPTION - PVC composite material comprises E-PVC paste layers, base coat layers and high-strength polyester sandwiched fabric, where the base coat layers are formed by coating the top and bottom surfaces of the high-strength polyester sandwiched fabric with base coat layer coating liquid and then performing drying, plasticizing and cooling; the E-PVC paste layers are formed by coating the base coat layers on the top and bottom surfaces of the high-strength polyester sandwiched fabric with E-PVC paste layer coating liquid and then performing drying, plasticizing and cooling. The base coat layer coating liquid comprises 70 pts. PVC paste resin, 30 pts. PVC blending resin, 60-70 pts. diisononyl phthalate, 2-3 pts. liquid barium zinc stabilizer, 4-8 pts. flame retardant powder and 1-3 pts. viscosity modifier. The E-PVC paste layer coating solution includes 60 pts. PVC paste resin, 40 pts. PVC blending resin, 50-60 pts. diisononyl phthalate, 1-3 pts. ESO, 2-5 pts. powdered nitrile butadiene rubber, 3-6 pts. TPSiV resin, 1-3 pts. liquid barium zinc stabilizer, 1-3 pts. viscosity modifiers, and 0.1-0.3 pts. antioxidant. An INDEPENDENT CLAIM is also included for preparing the PVC composite material, comprising (i) adding the base coat layer coating liquid components into a mixer, stirring for 15-20 minutes to obtain a base coat layer coating liquid having viscosity of 6000-8000 cps; (ii) soaking powdered nitrile rubber and TPSiV resin powder in diisononyl phthalate and heating for 4-5 hours at 60 degrees C; then adding the other materials into a mixer, stirring for 15-20 minutes to obtain E-PVC paste layer coating liquid, having a viscosity of 4000-5000 cps; (iii) preheating high-strength polyester sandwiched fiber mesh in heating roller at 105-110 degrees C for 10-30 seconds, removing the impurities attached to the surface, and then by the transmitting device adding into a vertical coater containing base coat layer coating liquid, soaking for 15-30 seconds, then into the double-sided scraper device, controlling the strength of polyester fiber surface and a bottom surface of mesh folder paste volume to 100-125 g/m2, drying in vertical gradient temperature drying oven, plasticizing, to obtain surface coated base coat layer and bottom polyester mesh; where in the first gradient, drying at 100-120 degrees C for 25-35 seconds; second gradient, drying at 140-150 degrees C for 20-25 seconds; and third gradient, drying at 150-160 degrees C for 10-25 seconds; (iv) cooling the polyester mesh by passing chilled water; (v) adding the cooled polyester mesh into vertical second coater, immersing in E-PVC paste layer coating solution for 15-30 seconds, then adding into double-sided scraper device, then coating the high-strength polyester fibers paste bottom surface with 140-160 g/m2 E-PVC paste layer coating solution, carrying out vertical gradient temperature oven drying, and plasticizing, to obtain second polyester mesh; and (vi) cooling the secondary polyester fiber cloth using chilled water rollers.