A waterproof, airtight, anti-slit, high transverse tensile strength double-layer zipper made by: stitching a continuous polyester chain to a middle part of a broad-width fabric tape and then separating the continuous polyester chain into left and right series of interlocking teeth after zipper chain tape dyeing and drying and gluing processes, and then folding up the zipper chain tape and stitching up the open side of the folded zipper chain tape so as to obtain a single-sided double-layer zipper chain tape, and then using a zipper slider to couple two single-sided double-layer zipper chain tapes, thereby obtaining a waterproof, airtight, anti-slit, high transverse tensile strength double-layer zipper. Alternatively, the continuous polyester chain can be stitched to the broad-width fabric tape near its one lateral side for making a high-strength double-layer zipper with less fabric consumption.