The invention discloses an immersed pipe device of a medium-deep geothermal well. The device is placed at the bottom in an outer sleeve of the geothermal well, and comprises an upper section, a middlesection and a lower section; the upper section consists of inner sleeves; the middle section consists of a metal expansion joint, a nonmetal expansion joint and a fixed immersed pipe; and the lower section consists of a movable immersed pipe and a guide head connected in sequence. The movable immersed pipe and the fixed immersed pipe are connected through pipe inner and outer bosses; the bottom of the movable immersed pipe is connected with the guide head; the fixed immersed pipe is of a hollow structure, and a sandwich layer is filled with tungsten diselenide; the surface of the movable immersed pipe is coated with a tungsten diselenide film coating layer; multiple layers of jet holes with gradually increased apertures are formed in the peripheral direction from top to bottom; and a spiral rib is mounted on the inner side of the guide head. Through the mode of coating low-heat-conducting-coefficient materials on the sandwich layer and the coating layer, the heat transfer short-circuit degree of metal immersed pipes is reduced; and through the movable connecting mode of the fixed and movable immersed pipes, the bottom dead area range is shortened, and the contribution of a heat exchange well is greatly improved.