The invention discloses a solar-powered back plate. The solar-powered back plate comprises an inner surface layer, a core layer and an outer surface layer in the mass ratio of (10-20):(20-40):(40-60) from inside to outside, wherein the inner surface layer is made from vinyl resin, a filler and an additive; the outer surface layer is made from polyamide resin, a filler and an additive; and the core layer is made from a modified polyethylene resin composition. The invention further develops a novel polyethylene resin composition, which comprises 100 parts of crosslinked polyethylene resin, 0-50 parts of grafted polyethylene, 0.1-0.5 parts of catalyst, 0-100 parts of filler and 0-2.5 parts of additive. The novel solar-powered back plate developed by the invention is prepared through a coextrusion process; and a prepared final product has the advantages of superior adhesion, high interlaminar peeling strength, aging resistance, particular damp-heat aging resistance, low saturated water absorptivity, low water vapor transmittance and superior electric insulating property, simple preparation process, low cost and suitability for industrial production.