Abstract: The present disclosure discloses a fiber Bragg grating displacement sensor with positive and negative bidirectional measurement and free from vibration, which falls within the technical fields of fiber sensing and measurement monitoring, and aims to solve the problem that the measuring range of the existing fiber Bragg grating displacement sensor is positive, and the free end of the cantilever beam will generate vibration deformation, resulting in inaccurate displacement measurement. The sensor of the present disclosure has a positive and negative two-way displacement measurement range through the arrangement of a bidirectional measuring mechanism. In the measurement process, the cantilever beam of the vibration-avoiding mechanism is in an initial state of zero deformation, resulting in upper and lower bending deformation, so as to avoid the fatigue and failure problems caused by the cantilever beam and the fiber Bragg grating due to constant force.