The invention relates to a preparation method of a cellulose/nano attapulgite composite barrier film, and belongs to the technical field of natural macromolecule-based packing materials. The preparation method comprises the following steps: firstly, acidifying nano attapulgite to prepare acidified nano attapulgite, dispersing the acidified nano attapulgite in water to obtain a nano attapulgite suspension, mixing the nano attapulgite suspension with an alkaline solution to obtain a mixed solution, dissolving 4 to 8 weight percent of cellulose into the mixed solution at -30 DEG C, freezing, defreezing, stirring and centrifugally debubbling the solution, forming a film through tape casting, regenerating the film in solidification liquid to obtain hydrogel, washing the hydrogel with water tillthe hydrogel is neutralized, and drying the hydrogel to obtain the cellulose/nano attapulgite composite barrier film. The preparation method disclosed by the invention is environmentally friendly, easy to operate and high in process stability. The tensile strength of the prepared composite barrier film is more than or equal to 110 MPa, so that the composite barrier film is high in transparency and biodegradability, excellent in mechanical property and gas barrier performance, and particularly suitable for being used as a food packing material.