The invention discloses an unmanned ship routing inspection device for an offshore wind power plant and a method thereof. The unmanned ship routing inspection device comprises an unmanned ship body, a stabilizing mechanism, and a cleaning mechanism; the stabilizing mechanism comprises a transparent cover, a camera and a supporting component, the transparent cover is fixedly connected to the top of the unmanned ship body, the supporting component is arranged in the transparent cover, the supporting component is arranged at the top of the unmanned ship body, and the camera is arranged on the supporting component; according to the cleaning mechanism, a fixing motor rotates to drive a cleaning rod to rotate on the transparent cover for cleaning, meanwhile, a water pump conveys water to the cleaning rod, the transparent cover can be cleaned, and through cooperation of a supporting rod, a fixing ring and a fixing base, the situation that a camera swings greatly, the transparent cover is dirty, and the shooting effect is affected can be avoided; and through quick rebounding of mounting springs and fixing springs, a breathable plate is quickly restored to the original shape, the stability of internal devices is improved, and the air circulation speed is increased through rotation of a fan to dry the interior of the unmanned ship body.