Aiming at the problems that it is difficult to locate the faults such as cable aging and damage in coal mine, the cable fault location technology based on frequency domain reflection method is studied. Inject a frequency domain signal into the cable and obtain the waveform of the reflected signal, windowing the signal, distinguish the fault type of the cable according to the waveform change of the reflected signal, and locate the fault point according to the transmission speed of the signal in the cable. The non-destructive location and on-line monitoring of cable fault in coal mine are realized.