The invention relates to a fixing device for an overhaul cover of a high voltage device box. The fixing device comprises a box body of the device box and the overhaul cover. The overhaul cover is fixed to the box body through an interlocking mechanism, and the interlocking mechanism is composed of a lock device, a rotating mechanism, a locking mechanism and an unlocking mechanism. A key of a high voltage device box is inserted into the lock device, the lock device is connected with the rotating mechanism and controls the rotating mechanism to lock the opening or closing state, the rotating mechanism controls the locking mechanism to move to lock or unlock the overhaul cover, and the locking mechanism is unlocked through the unlocking mechanism. The fixing device for the overhaul cover of the high voltage device box is reliable in structure and simple to operate. The interlocking mechanism is arranged between the overhaul cover and the box body, uniqueness of opening the overhaul cover of the high voltage device box is ensured, safety of overhaul personnel is ensured when the overhaul cover of the high voltage device box is opened, and safety accidents caused by misoperation are avoided.