The invention provides a use method of a double-layer zipper. The double-layer zipper comprises a zipper base and zipper strips. The zipper base comprises a handle frame, a handle, an upper zipper base body and a lower zipper base body. The zipper strips comprise the upper zipper strip, upper zipper cloth, the lower zipper strip and lower zipper cloth. The upper zipper cloth is connected with the upper zipper strip, and the lower zipper cloth is connected with the lower zipper strip. During use, the double-layer zipper is arranged on a trunk or a luggage bag, the double-layer zipper is provided with the upper zipper strip and the lower zipper strip, and an opening of the trunk or the luggage bag is sealed through the double-layer zipper; when the trunk or the luggage bag is impacted, the upper zipper strip and the lower zipper strip disperse impact force of the opening of the trunk or the luggage bag, cracking of the opening of the trunk or the luggage bag is avoided or relieved, and the strength of the zipper is improved; meanwhile, the antitheft performance of the trunk and the luggage bag is improved, and the difficulty that a lawbreaker inserts an edge tool into a zipper to unfasten the zipper is increased.