In order to solve the problem of displacement monitoring of health monitoring system in the complex electromagnetic environment, and realize the real-time monitoring of large mechanical and engineering struc-ture health and safety conditions, a novel fiber Bragg grating displacement sensor based on the structure of the cantilever beam is designed. Two fiber gratings with different central wavelengths are symmetrically pasted on the both sides of the cantilever beam. When the free end of the cantilever beam is changed, the two fiber grat-ings are respectively subjected to tension and pressure, which leads to the drift of the gratings center wavelength to the opposite directions. Through demarcating the relationship between the two center wavelength difference and displacement, it is possible to realize the measurement of the displacement. At the same time, the problem of cross sensitivity between temperature and displacement is solved. The sensor adopts draw-wire type dis-placement transmission mode, which makes the sensor installation location and measurement method more flexible. In addition, a smart device used to change the measuring range of the sensor is designed and it is also easy to be assem-bled and disassembled, so the whole sensor can be widely used. The experimental results show that when the range is 60 mm, the average sensitivity of the displacement sensor is 47.7 pm/mm，the correlation coefficient is 0.998, the repeatability error is 2.83% FS and the hysteresis error is 1.02% FS. The displacement sensor is char-acterized by simple structure and adjustable range, which can meet the demands of displacement measurement under different environments.