The invention discloses a cladding optical attenuator which comprises a double-cladding optical fiber with a section of outer cladding being stripped and a radiating clamp. The radiating clamp comprises a U-shaped groove and a radiating channel, and the radiating channel is placed at the bottom of the U-shaped groove and is parallel to the U-shaped groove. The section with the outer cladding being stripped of the double-cladding optical fiber is placed at the bottom of the U-shaped groove, and is fixed through coating materials with the refractive index being higher than or equal to the refractive index of a cladding in the double-cladding optical fiber. The coating materials of high refractive index are used, cladding light can be stripped within a finite length, and the quality of light beams of an optical fiber laser is improved; the radiating clamp is used for conducting cooling processing due to the fact that the coating materials of the high refractive index are used for absorbing heat generated by the cladding light on the cladding light stripping portion, the temperature of the coating materials is effectively lowered, the high stripping efficiency of the optical attenuator is guaranteed, and the stable work of the system is guaranteed.