The invention relates to a mobile robot structure, in particular to a mobile robot being applicable to large span transmission line routing inspection, which comprises a front upper arm, a rear upper arm, a front lower arm, a rear lower arm and an electrical appliance box body, wherein one ends of the front and the rear lower arms are respectively installed on the electrical appliance box body, the other ends of the front and the rear lower arms are respectively and rotatably connected with one ends of the front and the rear upper arms through a front and a rear rotation mechanisms, and the other ends of the front and the rear upper arms are respectively provided with a travelling mechanism which travels on a transmission line and a clamping mechanism which clamps the transmission line; and the front and the rear rotation mechanisms have the same structure, and respectively comprise a rotation pair and a spring, one ends of the two upper arms of the mobile robot are respectively and rotatably connected with the other ends of the two lower arms of the mobile robot through the rotation pairs, and the springs which can rotatably reset the upper arms are arranged between the upper arms and the lower arms of the mobile robot. The mobile robot has the advantages of large climbing angel, off-line prevention, good safety protection, short obstacle navigation time, simple obstacle process, fault release function, wider application scope and the like.