The utility model discloses a misoperation preventive device for power transmission lines. The misoperation preventive device comprises a signal generator, a power coil, a measuring coil, a filter circuit, an A/D (analog/digital) converter, a judging module and indicator lamps. The connection structure of the misoperation preventive device includes that the power coil is sequentially connected with the signal generator, the judging module and the indicator lamps, the measuring coil is sequentially connected with the filter circuit, the A/D converter, the judging module and the indicator lamps, and the power coil and the measuring coil are sleeved on a down conductor. The misoperation preventive device has the advantages that grounding conditions of the lines can be detected before the maintained lines are switched on, and switch-on failure due to the fact that the lines with ground wires are switched on is prevented; and whether the lines have ground points or not can be directly judged according to detection results.