A reversing valve, and an assembly method of the reversing valve. The reversing valve includes: a main valve including a first valve body and an adapter tube, the first valve body having a first valve cavity, and one end of the adapter tube being in communication with the first valve cavity; a pilot valve including a second valve body and a capillary tube, the second valve body having a second valve cavity, a first end of the capillary tube being in communication with the adapter tube or the first valve cavity, and a second end of the capillary tube being in communication with the second valve cavity; and a sleeve, wherein a side wall of the adapter tube is provided with a first mounting hole in communication with an inner hole of the adapter tube; the first valve body is provided with a second mounting hole in communication with the first valve cavity; the sleeve passes through the first mounting hole or the second mounting hole; and the first end of the capillary tube passes through the sleeve.