The invention relates to a biodegradable thermoplastic starch resin film which is prepared from, by mass, 40-52% of thermoplastic starch, 8-16% of metallocene, 20-30% of low-density polyethylene, 3-5% of a slipping agent, 4-6% of high-density polyethylene and 5-8% of pigment.A preparation method of the biodegradable thermoplastic starch resin film includes the following steps that the thermoplastic starch, metallocene, low-density polyethylene, the slipping agent, high-density polyethylene and pigment are subjected to mixing through a mixing mill according to the mass percent, the mixture is added into a film-blowing unit, processes of plasticizing, extrusion, blowing up, traction and rolling-up are conducted through a film-blowing and extrusion machine, and the biodegradable thermoplastic starch resin film can be obtained through blowing.Compared with the prior art, special raw materials including environmentally friendly biological polyethylene are adopted, so that the produced film is biodegradable and biologically environmentally friendly, and emission of carbon dioxide is reduced.