The invention provides a methylbenzene-polyvinyl alcohol degradable plastic film composition and a preparation method thereof, and relates to the technical field of film production. The methylbenzene-polyvinyl alcohol degradable plastic film composition is prepared from the following raw materials in parts by mass: 100-110 parts of chlorosulfonated polyethylene, 2-3 parts of gas-phase white carbon black, 3-5 parts of titanium dioxide, 5-10 parts of disproportionated rosin, 2-3 parts of TOTD, 2-3 parts of ethylene thiourea, 15-20 parts of epoxy resin, 2-5 parts of tetramethylthiuram tetrasulfide, 60-70 parts of polyvinyl alcohol, 15-20 parts of artemisia glue, 12-18 parts of hydroxypropyl cellulose, 7-15 parts of Pulullan, 13-16 parts of nano silicon dioxide, 15-20 parts of zinc stearate, 14-18 parts of oxidized polyethylene wax, 12-17 parts of ethyl silicon oil, 13-15 parts of calcium carbonate, 4-10 parts of glutaric dialdehyde and 13-15 parts of stearyl alcohol. The plastic film prepared by the invention is photodegradable and biodegradable, and can effectively solve the problem that a common plastic film is nondegradable so as to cause white pollution.