The embodiment of the utility model discloses a locking device of a wire cavity cover plate, comprising a wire cavity body, a wire cavity cover plate, a rotating shaft, a spanner rotating shaft, at least one spanner and at least one spanner clamping pin nail. One end of the wire cavity cover plate is connected with the wire cavity body through the rotating shaft, the spanner comprises a spanner body and a spanner clamp, the other end of the wire cavity cover plate is connected with the spanner body of the spanner through the spanner rotating shaft, the spanner clamping pin nail is fixed on the wire cavity body, and the spanner clamping pin nail and the spanner clamp are used for clamping the spanner clamping pin nail with the spanner clamp to lock the wire cavity cover plate and the wire cavity body. The locking device of the wire cavity cover plate, which is provided in the utility model, can be utilized for locking the wire cavity cover plate without screws in a locking process. Without carrying or using screw-locking tools, the utility model has convenient operation, improved mounting efficiency of mounting staff and strong universality.