The utility model provides an optic fibre defect detecting device, optic fibre defect detecting device includes: data processor, pulse laser, time data converter and light detector, pulse laser for under data processor's control, to being sent the laser pulse signal by test optic fibre, light detector for whether detect is had the reverberation of production signal by test optic fibre at transmission laser pulse signal in -process, when light detector detects the reverberation signal, to time data converter transmitting trigger signal, the time data converter for record pulse laser sends the very first time of laser pulse signal, and receives triggering signal's the second time, and sends the very first time and second time to data processor, data processor for time difference and light propagation velocity according to the very first time and second time calculate the defect position that reachs by test optic fibre. This optic fibre defect detecting device is used, convenient, short -term test to the optic fibre defect can be realized.