The invention discloses a high-strength easily degradable modified polyethylene film and a preparation method thereof and belongs to the technical field of easily degradable modified polyethylene films. The formula in the invention comprises polyethylene, ultra high molecular weight polyethylene, glass fibers, hydrophilic modified polyurea coated nanometer copper oxide mimic enzymes, octacalcium phosphate, nano-zinc oxide, N,N-methylene bisacrylamide, triethylene tetramine, an epoxy silane coupling agent, poly(vinyl ether), propylgallate, a glycidyl methacrylate grafted octylene-ethylene copolymer, maleic anhydride, polylactic acid, carboxymethyl starch, citric acid and a plasticizer. The polyethylene and nano powder are subjected to green and low-energy-consumption compatibility, hydrophilcity, reinforcing and toughening, photocatalysis and thermal oxidation promoted modification, and by virtue of the technical means of one-step cold grinding modification and further repeated melt co-extrusion modification, the modified polyethylene is prepared. The prepared modified polyethylene has synchronously enhanced mechanical property and good degradation property, and the process is simple, low in cost and easy for industrial production.