The invention relates to a butt-joint pipeline welding robot, and belongs to the field of industrial robots. The butt-joint pipeline welding robot is composed of a welding trolley and a welding gun adjusting mechanism arranged on the side face of the welding trolley, wherein the welding trolley comprises a driving device and a trolley body, and the welding gun adjusting mechanism comprises a horizontal swinging mechanism and a vertical adjusting mechanism. The welding trolley can be firmly adsorbed to a welded pipeline through permanent magnet idler wheels, the driving motor of the welding trolley is controlled through a handheld controller, and then the permanent magnet idler wheels are controlled to drive the welding trolley to crawl along the welding joint of the welded pipeline; the driving motor of the welding gun adjusting mechanism is adjusted in real time by observing the position offset condition between a welding gun and the welding joint center to adjust the left-right offset position of the welding gun and the height, away from the welding joint, of the welding gun.