The invention discloses a sleeving, bending and forming tool for a thin-wall copper pipe. An inner pipe is supported by a part of a mandrel module, an outer pipe is supported by the other part of themandrel module, and the lengths of mandrels of two parts can be adjusted according to production needs; a clamping module adopts an adjustable compression structure, and can not only position the assembly dimensions of the outer pipe and the inner pipe, but also be used for positioning and clamping the inner pipe; and with the help of bending work of a pipe bending die, a guide sliding plate and acompression block, the bending forming process of the thin-wall copper pipe is improved. By supporting and fixing the inner pipe and the outer pipe at the same time, the supporting position is adjusted according to the actual clearance, and then the inner pipe and the outer pipe are simultaneously clamped for conventional bending; there is no need to use rosin for filling, two ends do not need blockage welding, and the machining cycle and the quantity of accessory materials are saved; because the interior and the gap between the two pipes are supported, the forming quality defects such as pipe fitting breakage, wrinkling and dead bending are avoided in the forming process; and the circular degree is not out of clearance after a part is machined.