The invention discloses an optical fiber channel failure detecting device which comprises a pulse generator, a laser device, a coupler, an optical detector, an amplifier, an oscilloscope and a time base circuit. The pulse generator is connected with the laser device which is connected with the coupler, the coupler is connected with the optical detector which is connected with the amplifier, the amplifier is connected with the oscilloscope, the time base circuit is connected with the oscilloscope and the pulse generator, and the coupler is provided with an optical fiber interface used for being connected with a to-be-detected optical fiber. The optical fiber channel failure detecting device has the advantages that judgment on short-distance tail fiber failure and judgment on long-distance optical fiber channel failure can be realized to achieve the objective of quickly and accurately judging optical fiber channel failure position.