Aiming at the problem of low signal sampling rate and signal processing speed of linear frequency modulation continuous wave displacement sensor, this paper designs a fiber optic displacement sensor with a Fabry?Perot interferometer structure based on STM32H743 chip. The optical fiber displacement sensor uses sawtooth wave to modulate the frequency of the laser, and selects STM32H743 as the core processor to improve the signal acquisition and processing speed. Its main frequency is 400 MHz, and the analog to digital converter maximum conversion rate is 4.5 MHz. Combined with frequency modulated continuous wave laser interferometry, the displacement of stainless steel pipe with fixed cavity length and moving target is measured. Experimental results show that in the 200?400 mm measurement experiment, the standard deviation of the measurement result of 1 mm/s is less than 3.3 nm, and the linear fitting coefficient in the range of 600 mm is above 0.99998, which has a good application prospect in the field of displacement measurement.