The invention discloses a seaming method for large and small nylon chain racks and a double-layer-teeth chain tape structure, aiming at providing the seaming method for the large and small nylon chain racks and the double-layer-teeth chain tape structure which have the advantages that the anti-burglary property is good, the service life is long, and the seaming is convenient. The seaming method is characterized by comprising the following steps: first, carrying out first-time seaming on a cloth tape matched with the large chain rack and the small chain rack, wherein a used seaming thread corresponds to the common seaming thread for seaming the small chain rack; and seaming the large chain rack to the other surface, opposite to the small chain rack, of the cloth tape, and carrying out the second-time seaming, wherein the seaming thread corresponds to the common seaming thread for seaming the large chain rack, and the seaming thread for the second-time seaming is positioned on the cloth tape on the outer side of the small chain rack. With the method and the structure provided by the invention, the difficulty in seaming the upper-layer and lower-layer chain racks with the specifications differing greatly on the cloth tape is effectively solved, and meanwhile, positive effects are expected to be achieved for the popularization and use of the double-layer-teeth zipper with the wide upper part and the narrow low part.