The invention discloses a fiber irradiation monitoring device and method. The device comprises an irradiation fiber, a broadband spectrum light source, an irradiation bleaching laser light source, a fiber time domain reflection instrument and a beam combiner, wherein the broadband spectrum light source is used for acquiring absorption loss spectrum after irradiation fiber irradiation and photobleaching and measuring the accumulated dose and the close rate of the irradiation fiber through analyzing spectrum types and intensity change before and after irradiation, the irradiation bleaching laserlight source is used for bleaching the irradiation fiber after irradiation, and the fiber time domain reflection instrument is used for monitoring the nuclear radiation leakage position and background loss of the fiber. The device is advantaged in that wavelength and power of the irradiation bleaching laser light source are adjusted through the loss spectrum fed back by the broadband spectrum light source, photobleaching of the irradiation fiber is carried out, irradiation-induced defects are eliminated, irradiation-induced loss is reduced, fiber irradiation saturation is avoided, and great prolongation of irradiation fiber service life and replacement frequency reduction are realized.