The utility model relates to the technical field of subway power supply system interval system cable laying. The special semi-arc-shaped protection device for preventing the cable from being scratchedfor the subway is provided. U-shaped flat steel, a semi-arc-shaped chopping board and an insulating pad, the U-shaped flat steel is transversely arranged and is fixedly connected with the baffle sidebracket to form a planar closed space; a through hole is formed in the bottom of the U-shaped flat steel; the inner surface of the semi-arc-shaped chopping board is fixedly connected with a bolt; wherein the semi-arc-shaped chopping board is fixedly arranged above a lower transverse plate of the U-shaped flat steel through the bolt, the insulation pad is fixedly arranged on the outer surface of the semi-arc-shaped chopping board, and the cable is arranged above the insulation pad and located in a space defined by the U-shaped flat steel and the baffle side support. The protection device is good in protection effect, not prone to disengagement in the later period, convenient to maintain in the later period, simple in structure, low in manufacturing cost, light and convenient to carry, easyand convenient to install and capable of guaranteeing the construction quality, and has certain popularization value and use value.