A plasticized biodegradable polyester film formed from a biodegradable polyester in approximately 100 parts by weight, a plasticizer in from approximately 5-25 parts by weight, an inorganic filler in from approximately 0-150 parts by weight; and an antioxidant in from approximately 0.1-1 parts by weight. A method for preparing the plasticized biodegradable polyester film including drying the biodegradable polyester, drying the inorganic filler, mixing the biodegradable polyester, the plasticizer, the inorganic filler and the antioxidant, adding the mixed biodegradable polyester, plasticizer, inorganic filler and antioxidant into an extruder forming extruded plasticized biodegradable polyester material, drying the extruded plasticized biodegradable polyester material, and blowing the dried plasticized biodegradable polyester material as a master batch into film through a extruder to obtain the plasticized biodegradable polyester film.