The invention provides a double-wall corrugated pipe and an external pipe thereof. The double-wall corrugated pipe and the external pipe thereof mainly comprise the double-wall corrugated pipe and the external pipe. Compared with a common corrugated pipe, the double-wall corrugated pipe is characterized in that the external surface of the pipe adopts a helical line. The external pipe is of a thin-walled cylinder of which the inner wall is provided with a helical line, and the size of the helical line of the inner wall is just matched with the size of the helical line of the external surface of the double-wall corrugated pipe. The external pipe is matched with the double-wall corrugated pipe together in a manner of screwing in from one end. A connecting ring and a connecting wall are respectively arranged at the two edges of the pipe, and a sealing groove is formed in the connecting ring. At the same time, the external pipe is added, so that the double-wall corrugated pipe is more conveniently connected. Due to the more usages of the external pipe, the pipe is manufactured to be longer and mounted on the whole pipe in a sheathing manner, and the effect of strengthening the strength of the pipe is achieved.