The utility model provides a power failure warning device of special power supply loops for a ventilator, which comprises an underground transformer substation, a ventilation and prevention monitoring substation, an underground scheduling substation, a mining KT33 adapting substation, a mining equipment on-off sensor, a UPS (uninterrupted power supply) and a power supply loop not special for the ventilator, wherein the mining KT33 adapting substation is a core piece, is simultaneously upwards connected with the underground transformer substation and the ventilation and prevention monitoring substation, and is simultaneously downwards connected with the underground scheduling substation and the mining equipment on-off sensor; and the mining equipment on-off sensor is simultaneously connected with the UPS and the power supply loop not special for the ventilator. When one loop is power off, current signals are directly output by the equipment on-off sensor and transmitted to a '555' integrated block to be amplified and converted, an SCR (silicon-controlled rectifier) is switched on to drive a direct current relay to act; after the relay acts, the relay drives three normally open contacts to be closed, so the aim and the requirement that operators on duty in three monitoring places can constantly monitor the power supply phenomena in all weather are achieved. The power failure warning device has the advantages that the integral structure is simple, the operation and the use are convenient, and the stability and the reliability are high.