The invention relates to a cable-climbing robot used for detecting poly ethylene (PE) damage on the surfaces of cables in a suspension bridge and a cable-stayed bridge, wherein the cable-climbing robot comprises a driving trolley (1) and a driven trolley (2) which are arranged symmetrically on the left and right sides; both the driving trolley (1) and the driven trolley (2) are provided with two wheels (7) and connected with each other through a connecting piece; a four-connecting-rod tensioning mechanism (9) is arranged on the driven trolley (2) and comprises four connecting rods (13), an adjusting screw rod (14), an adjusting nut and an adjusting spring (12); a climbing mechanism is arranged on the driving trolley (1) and comprises one pair of helical gears with matched right angles, a direct current motor (5) and a transmission chain (6); And V-shaped grooves are arranged on the wheels (7) of the driving trolley (1) and the driven trolley (2). The cable-climbing robot is applied to the surfaces of various cables used at present and is suitable for operation condition in high air; the commonality is good; rechargeable batteries are adopted for providing power; and the cable-climbing robot has simple structure design, and is convenient in maintenance and safe and reliable in operation.