An optical-fiber atomic light-filtering apparatus comprising an optical-fiber coupling focusing collimating mirror, a first polarizing optical fiber, a first permanent magnetic ring, a pure iron frame shaped like the Chinese character “”, a heat preservation box, a first capillary atomic cell, an armored twisted-pair heating wire, a second permanent magnetic ring, a second polarizing optical fiber, a thermostat, a cable, a third permanent magnetic ring, a temperature sensor, a second capillary atomic cell, a fourth permanent magnetic ring, a third polarizing optical fiber and a photoelectric detector. The two pairs of permanent magnetic rings are matched with the pure iron frame shaped like the Chinese character “” to provide magnetic fields for the two capillary atomic cells working in the same temperature environment; a polarizing plane changes after interaction between a weak signal light and atoms.