A non-contact FBG displacement self-calibration device is studied using the non-contact force transmission characteristics of magnets, with FBGs as the core component, a cantilever I-beam and permanent magnets as auxiliary components to solve the problem that the fiber Bragg grating displacement sensors are susceptible to temperature and vibration and other external factors leading to poor measurement repeatability. Self-calibration of position information is performed using the maximum magnetic force applied to the I-beam when the position of the magnet at the moving end coincides with that of the magnet at the position calibration end, which in turn improves the measurement repeatability and measurement accuracy of the FBG displacement sensor. By mountings self-calibration device on the displacement sensor of the tape measure structure, the sensing characteristics of the device are studied experimentally and the results show that the average root-mean-square error before calibration is 5.838mm, and the average root-mean-square error after calibration is 0.953mm over the measurement range of 0~360 mm. The self-calibration device used in this paper greatly improves the measurement repeatability of FBG displacement sensor, which provides a new method for the optimization of environmental adaptation of displacement sensors.