The invention discloses a preparation method of a boron fiber modified chitosan degradable film, belonging to the field of packaging film preparation. The preparation method is characterized by comprising the following steps of heating and mixing a boric acid solution and melamine, standing and filtering to obtain a filter cake, grinding the filter cake, then calcining a product in a graphite vacuum furnace, then heating a product in a muffle furnace to obtain boron fibers, mixing the boron fibers with gamma-aminopropyltriethoxysilane and absolute ethyl alcohol, adding chitosan powder and an acetic acid solution after filtering and drying, fully dissolving the materials, then heating and mixing a product and an epoxy polymerization liquid, standing for defoaming, then carrying out film casting, soaking a film in a sodium hydroxide solution and a hydrochloric acid solution respectively, washing the film with deionized water and drying the film, thus preparing the degradable film. The preparation method has the beneficial effects that the preparation method is simple; the toughness of the obtained product is higher than that of other packaging films by 18%; the tensile strength of the product is not less than 11.5MPa; the elongation at break of the product is not less than 250; the water vapor barrier property is good after film forming; after being used and abandoned, the product can be naturally degraded, does not cause white pollution and is safe and environmentally friendly.