The invention discloses a release film for a car cover, and a preparation method of the release film. The release film comprises a PET base layer, which is sequentially provided with a pressure-sensitive adhesive layer, a release layer and a protective layer, wherein the protective layer comprises benzoate, turpentine, butanone, methylbenzene, nano metal oxide, sodium hydrogen sulfate and an ultraviolet ray absorber, the release layer is prepared from an isocyanate curing agent, butyl acetate, a prepolymer resin, methyl hydroquinone, 2-hydroxymethyl oxetane and dodecyl glycidyl ether, and thepressure-sensitive adhesive layer is prepared from nano-scale SiO2 powder, an epoxy acrylic curing agent, ethyl acetate and dimethyldiethoxysilane. According to the invention, an ultraviolet ray absorber is added in a protective layer, so that ultraviolet ray can be completely blocked, harm of the ultraviolet ray to human bodies is avoided, the service life is long, the definition is good, and a certain explosion-proof effect can be achieved on the automobile glass.