The invention relates to a completely-biodegradable film bag material and a preparation method of a film bag. The completely-biodegradable film bag material is prepared from mixing the following raw materials in parts by weight: 50 to 70 parts of PBAT (poly-butylene
adipate-co-terephthalate), 5 to 20 parts of PLA (poly-
lactic acid), 0.3 to 2 parts of a compatilizer, 1 to 5 parts of a
plasticizer,5 to 35 parts of modified filler, 0.2 to 1 part of an anti-
hydrolysis agent, and 0.5 to 2 parts of a dispersant, wherein the modified filler is prepared by adding an
inorganic filler or organic fillerinto a mixing
machine, stirring, sequentially adding a surface modifying additive in the stirring process, and mixing. When the modified filler is added into the material, the property of the film bag product is not degraded; however, the production cost is greatly reduced. The completely-biodegradable film bag material and the preparation method of the film bag has the advantages that the production technology is simple; the forming stability, opening property,
puncturing-resistant property, dispersing property of color master batch are good; the surface is smooth, and the completely-biodegradable film bag material can be used for producing shopping bags, rolling bags, express bags, garbage bags and the like.