The invention relates to a vehicle-mouthed overhead cable layout device. The vehicle-mouthed overhead cable layout device comprises a front support movably connected with the top of a vehicle body. The upper portion of the front support is movably connected with the upper portion of a rear support, the lower portion of the front support is movably connected with a supporting hydraulic oil cylinder, and the supporting hydraulic oil cylinder is located on a hydraulic oil cylinder installation plate. A rear support fixing base is fixed to the portion, on the opposite side of the front support, of the top of the vehicle body. A hand wheel and a pulley are arranged on the front support, and a steel wire rope is erected between the handle wheel and the pulley. By implementing the technical scheme, the cable supports are installed on the top of a bypass operation cable vehicle and are lifted or retracted through the hydraulic oil cylinder, and the vehicle-mouthed overhead cable layout device has the advantages of being high in adaptability and convenient to carry and saving labor in operation. The vehicle-mouthed overhead cable layout device is especially suitable for laying bypass cables just by arranging a steel wire rope in the middle of a temporary erected tower, and is fast to use and convenient to carry.