Abstract: The accuracy of absolute distance measurement is of great significance to the fields of aerospace technology, precision equipment processing, satellite formation, and planetary space positioning. The frequency sweeping interferometry (FSI) ranging technology based on tunable lasers has become an international research hotspot in recent year. It has the advantages of breaking 2π ambiguity, no dead zone of measurement, non-touch and independent of guide rail. The principle of FSI ranging, types and performance of some devices in the ranging system were briefly introduced, such as tunable lasers, detectors, etc. The factors that affect the uncertainty of the ranging system, including non-linear frequency sweep, Doppler frequency shift, dispersion mismatch, etc. were analyzed. Corresponding compensation methods for influencing uncertainty factors were discussed, and measurement results after compensation were compared and summarized.