A full-biodegradable plastic membrane, which uses thermoplastic starch with diameter of 1-9 mu m, biodegradable polymer and auxiliary component as raw material, processed by screw extruding apparatus and membrane producing apparatus. The raw material comprises 30-70 parts by weight of thermoplastic starch with diameter of 1-9 mu m, 10-40 parts by weight of biodegradable polymer, 5-10 parts by weight of compatible modified component, 3-5 parts by weight of complex plasticized component, 10-30 parts by weight of lubricant. These materials are mixed and processed by screw extruding apparatus and membrane producing apparatus, wherein the lubricant is at least adding into other materials for mixture before process by screw extruding apparatus and during melt blending, and the adding amount of lubricant before process by screw extruding apparatus is not more than 1 / 3 of the total amount thereof. By highly increasing dosage of lubricant and changing mixing way, thermoplastic degree of starch is increased, rheological property of the system and processing quality of product are dramatically improved, mechanical property of the product is enhanced.