A double-layer nylon zipper includes two zipper tapes each having two series of teeth respectively disposed at opposing top and bottom sides of the fabric strip thereof, and a zipper slider coupled between the interlocking series of teeth of the two zipper tapes and having opposing top guard frame wall and bottom guard frame wall, a division wall between the top and bottom guard frame walls, a nose located on the top guard frame wall and a pull tap coupled to the nose. The top guard frame wall and bottom guard frame wall have respective first ends kept in flush and respective second ends in different lengths so that an accommodation space is defined right below the second end of the top guard frame wall outside the second end of the bottom guard frame wall to facilitate smooth interlocking of the interlocking series of teeth.