The utility model discloses an on-line fence monitoring device based on optical fiber micro-bend loss. The device comprises optical fiber clamps and a fence rod, each optical fiber clamp is composed of an upper cover and a base, the bottom of each upper cover is provided with upper cover wavy teeth, the top of each base is provided with base wavy teeth, the upper cover wavy teeth and the base wavy teeth are arranged in the way that tooth tips correspond to grooves, detection optical fibers are clamped between the upper cover wavy teeth and the base wavy teeth, the upper covers are fixed on the fence rod, the detection optical fibers are clamped between the upper cover wavy teeth and the base wavy teeth in a back-and-forth manner, the device comprises two optical fiber clamps, and the two upper covers thereof are symmetrically distributed at two sides of the fence rod and are fastened on the fence rod by screws through fixed mounting holes on the upper covers. The on-line fence monitoring device based on optical fiber micro-bend loss has the advantages of being high in sensitivity, simple in structure, easy to assemble, commissioning-free, maintenance-free and capable of simplifying field construction and installation steps and reducing the cost.