NOVELTY - Back plate comprises polyethylene resin composition layer as an upper surface layer, polyolefin resin composition layer as a core layer and polypropylene resin composition layer as a lower surface layer in a mass ratio of 10-20:60-80:10-20. The polyethylene resin composition comprises polyethylene resin or ethylene vinyl acetate copolymer resin, pre-treated filler and additive. The pre-treated filler is obtained by treating the filler with silane coupling agent. The additive is antioxidant, UV absorbent and/or light stabilizer.    USE - The back plate is useful for solar energy battery module.    ADVANTAGE - The back plate has excellent adhesive properties, interlaminar peeling strength and electrical insulation properties, high temperature thermal aging resistance and humidity aging resistance, low saturated water absorption coefficient, low temperature impact resistance and low water vapor permeability.    DETAILED DESCRIPTION - Back plate comprises polyethylene resin composition layer as an upper surface layer, polyolefin resin composition layer as a core layer and polypropylene resin composition layer as a lower surface layer in a mass ratio of 10-20:60-80:10-20. The polyethylene resin composition comprises 100 pts. wt. polyethylene resin or ethylene vinyl acetate copolymer resin, 10-50 pts. wt. pre-treated filler and 0.1-5 pts. wt. additive. The polypropylene resin composition comprises 100 pts. wt. of polypropylene resin, 10-50 pts. wt. pre-treated filler and 0.1-5 pts. wt. additive. The polyolefin resin composition comprises 100 pts. wt. component A and 20-100 pts. wt. component B, 10-50 pts. wt. pre-treated filler and 0.1-5 pts. wt. additive. The pre-treated filler is obtained by treating the filler with silane coupling agent. The additive is antioxidant, UV absorbent and/or light stabilizer, and has density of 0.941-0.959 g/cm3. The component A is polypropylene homopolymer and/or polypropylene block copolymer, and has differential scanning calorimetry melting point of 160-165 degrees C, melt flow rate of 1-2 g/10 minutes. The component B is polyethylene homopolymer and/or polyethylene copolymer, and has differential scanning calorimetry melting point of 120-135 degrees C, melt flow rate of 1-2 g/10 minutes. An INDEPENDENT CLAIM is included for preparing the back plate comprising uniformly mixing the polyethylene resin composition, polyolefin resin composition and polypropylene resin composition, adding the mixture into a three-layer co-extruded sheet screw unit, then carrying out melt extrusion process, casting the extruded product, cooling the cast product, and then drawing and winding.