The invention belongs to the field of power detection equipment, and particularly relates to a power failure detection device. The device comprises a liquid fault detector for contact with a user sidecircuit and a color sensor for sensing the liquid fault detector, the color sensor is connected with an electric control main board, the electric control main board is provided with a communication interface, the communication interface is wirelessly connected with an alarm, the liquid fault detector comprises a detector sealing tube for containing the liquid which changes color when being heatedand high-heat-conductivity insulating columns arranged at two ends of the detector sealing tube, one end of the high-heat-conductivity insulating column extends into the detector sealing tube, and the other end of the high-heat-conductivity insulating column is in contact with the user side circuit. According to the heating characteristic of a faulty line of the user side circuit, the arrangementof the liquid fault detector being matched with the color sensor is provided, and the line fault is effectively and timely alarmed through wireless communication, so that the service quality of a power supply company is ensured, and the power consumption quality of residents is guaranteed.