Abstract: A displacement sensor for a frequency modulation continuous wave laser interference optical fiber, comprising a single mode frequency modulation continuous wave laser (1) and at least one optical fiber displacement sensing system; the optical fiber displacement sensing system comprises an optical circulator (2), an optical fiber collimator (3), a partial reflector (4), a cooperative reflector (5) and a photoelectric detector (6); the single mode frequency modulation continuous wave laser (1) is connected to an incident port of the optical circulator (2) by means of a single mode optical fiber or an optical fiber coupler; an adjacent emergent port of the optical circulator (2) is connected to the optical fiber collimator (3) by means of the single mode optical fiber; a third port of the optical circulator (2) is connected to the photoelectric detector (6).