In order to solve the problem of spectrum broadening of measurement signal and reduction of laser interference ranging accuracy caused by modulation nonlinearity of frequency modulated continuous wave (FMCW) laser. A frequency modulation interference ranging method based on equal optical frequency subdivision resampling is adopted. The waveform data after equal optical frequency subdivision resampling of the target signal at different positions by the double optical path ranging system is obtained and spectrum analysis is performed. The results show that the method of equal optical frequency subdivision resampling uses the subdivided clock signal points to resample the target measurement signal with a distance greater than the optical path difference of the auxiliary interference optical path, eliminating the influence of the modulation nonlinearity of the laser, and The problem of signal distortion caused by insufficient sampling points is avoided. The maximum residual error of the equal optical frequency subdivision resampling ranging system is less than ±18.46μm and the maximum measurement standard deviation is 23.39μm compared with the laser interferometer in the 4.3m measurement range. The auxiliary interference optical path used in this method has a short optical path difference and is less affected by the environment, so that a stable clock signal can be obtained and can reduce the size and cost of the double optical path FMCW ranging system. This study provides a practical reference for long-distance, high-precision frequency modulated continuous wave measurements.