The present invention relates to a mobile robot mechanism, in particular to a three-arm robot annular inspection mechanism, including front, lower, rear jaw mechanism, the front, lower, central and rear wheel swing arm mechanism, the front, lower, rear rocker One end of the connection mechanism by the rotation mechanism and the center wheel, the other end with the front, lower, front end of the trailing arm through the lower, rear tilt mechanism rotatably connected to the front, lower, rear swing arm means and the other end by the rotation of the front , the rear wheel rotatably connected to the pawl mechanism, the front, the other end of the rear running gear pawl mechanism is provided on a transmission line of travel and the clamp means clamp the transmission line; before, the same structure after the tilt mechanism comprising a drive motor and the swivel joint; before, the same configuration as the turning mechanism comprises a drive motor and a rotating pair. The present invention has the ability to cross the barrier complex drainage lines, able to adapt to the ground, conductor lines and other environments, it has a simple structure, strong obstacle ability, wide application range of advantages.