The invention discloses a washing device of a highway sound barrier. The washing device of the highway sound barrier comprises a hollow housing, a connecting column, a motor, a disc brush and a fixingframe. One end of the interior of the hollow housing is fixedly provided with the motor. The interior of the hollow housing at one side of the motor is provided with a minitype water pump. The outerwall at one end, adjacent to the motor, of the hollow housing is fixedly provided with a support body. A center position at one side, away from the hollow housing, of the support body is provided witha rotation cavity. The interior of the rotation cavity is provided with the disc brush. A center position at one side, adjacent to the support body, of the disc brush is fixedly provided with a rotation shaft. Two ends of the support body below the hollow housing are provided with the fixing frame. The bottom end of the fixing frame is fixedly provided with an anti-collision plate. The top end ofthe anti-collision plate is provided with a water collecting tank. The interior of the water collecting tank is fixedly provided with a filtering screen. A center position in the water collecting tank is provided with a water inlet pipe. The washing device of the highway sound barrier is capable of improving the working efficiency in a washing process, improving the convenience degree in the washing process, and realizing the cyclic utilization of water quality.