The invention discloses a detachable condensing tube for collecting biomass pyrolysis oil in order to solve the problems of consumption of a large amount of water source and electric energy, low utilization rate of cold energy, complex connection of pipelines, and tediousness in installation and use. The condensing tube includes a threaded cap, a barb, an inner tube fixing bracket, a double-layervacuum glass outer tube, a spherical glass inner tube, a glass tee and a collecting bottle; the spherical glass inner tube is mounted in the double-layer vacuum glass outer tube, the lower end of thespherical glass inner tube is in contact connection with the tail end of the double-layer vacuum glass outer tube, the inner tube fixing bracket sleeves the joint of the first inner tube bulb of the spherical glass inner tube and a gas discharge port, the T-shaped portion of the inner tube fixing bracket is connected with the barb on the inner wall of the double-layer vacuum glass outer tube, thethreaded cap sleeves the spherical glass inner tube and is in threaded connection with the double-layer vacuum glass outer tube, the outer wall of the tail end of the spherical glass inner tube is incontact connection with the inner wall of the inner tube interface of the glass tee, and the glass bottle interface of the glass tee is in contact connection with the bottle mouth at the upper end ofthe collecting bottle.