The invention belongs to the technical field of packaging of power lithium battery shells, and specifically provides a preparation method for an aluminum-plastic composite film. The preparation methodcomprises the following steps: preparation of a treatment layer: a step of cleaning the surface of an aluminum foil, carrying out drying, coating a surface treating agent onto the matte surface of the aluminum foil, carrying out a reaction under heating, and carrying out drying; coating a surface film-forming agent onto the other surface of the aluminum foil, and carrying out heating and drying so as to form a special protective layer; coating a polyurethane adhesive onto the treatment layer of the aluminum foil, then carrying out compounding with a film, and carrying out curing; selecting aswelling-resistant polypropylene or polyethylene modified particle material, adding a slipping agent in a certain proportion, carrying out full mixing, then adding an obtained mixture into a feed hopper of a screw extruder, and carrying out extrusion, wherein a thickness is controlled by control of the amount of extrusion and the rate of production, and an extruding and compounding process is adopted; and spraying an obtained material in a molten state onto the surface of the special protective layer of a cured aluminum-plastic composite film semi-finished product so as to complete a manufacturing process. The preparation method provided by the invention has the following effects: the disadvantage of insufficient impact molding performance of the aluminum-plastic composite film is solved;the chemical resistance of the aluminum-plastic composite film is greatly reinforced; and an outer protective layer has improved bonding effect and can bear strong stress concentration.