The invention discloses a three-point centered conducting rod assembling tool which comprises three supporting frames evenly distributed on the periphery of the assembling tool. Two adjacent supporting frames are connected with adjustable connecting mechanisms, the positions of the adjustable connecting mechanisms can be adjusted relatively, the three supporting frames are connected to form an annular framework, the outer lateral ends of the supporting frames of the annular framework are all connected with idler wheels which are in contact with the inner wall of a tube body to be installed, the inner lateral ends of the supporting frames are all connected with carrier plates, the carrier plates are in contact with a conducting rod which is arranged in the center of the tube body to be installed and are used for locating the conducting rod, the carrier plates are connected with the supporting frames through adjustable connecting mechanisms which can adjust the radial positions of the carrier plates, an installation groove is formed in the lateral side, in contact with the conducting rod, of at least one carrier plate of the three carrier plates, and a wedge for wedging the conducting rod is arranged in the installation groove. The distance between two adjacent supporting frames is adjustable, and the distances between the carrier plates and the supporting frames are adjustable. The three-point centered conducting rod assembling tool is suitable for different-diameter tubes to be installed and different-diameter conducting rods.