Aiming at the phenomenon of signal spectrum broadening and overlapping in short-range ranging of frequency-modulated continuous wave (FMCW) lidar, a multi-interference optical path ranging system based on FMCW was proposed. The signal frequency was reduced by improving the optical path structure to ensure the ranging accuracy. The problem of low signal-to-noise ratio (SNR) caused by spectrum overlapping was avoided, and the function of frequency reduction was realized, so that the low bandwidth detector could collect the high frequency interference signal. Measurement experiments were carried out for different distances from 0 to 30 m. The sampled data were processed by short-time Fourier transform to obtain high-precision micro-Doppler time-frequency graphs, and the frequency features were extracted and represented as corresponding distance information by calculation. The frequency resolution stability is improved by the structure from 28.3% to 4.4% in the range of 0 to 30 m, and the spatial resolution reaches ± 10 mm.