Objective Absolute laser ranging is widely used in scientific research and industry. Several types of absolute distance measurement methods can be used, such as the timeofflight method, phase ranging method, multiwavelength interferometry, and dualcomb ranging. The polarization laser ranging method is a phaseranging method that establishes the functional relationship among the laser polarization, modulation frequency, and measurement distance. As laser polarization is less susceptible to interference from environmental disturbances, the polarization laser ranging method can achieve higher precision than the phaseranging method. Laser polarization rangefinders have an irreplaceable role in fields such as assembly and inspection of large structural parts and field baseline construction. However, owing to technological monopoly and blockades, no independently developed laser polarization rangefinders 1404003 -9 研究论文 第 50 卷 第 14 期/2023 年 7 月/中国激光 are available in China. Research in universities and research institutes has mainly focused on system implementation and error analysis. The swing method is the only polarization laser ranging algorithm used in these studies. Waveform distortion would reduce the swing method accuracy; therefore, research on polarization laser ranging algorithms is necessary to improve ranging accuracy.Methods Based on the principle of polarization modulation ranging, the reason for waveform distortion and the influence of the local minimum point frequency accuracy on the ranging accuracy are studied. To obtain the minimum points of the demodulated signal, the swing and least square methods for polarization laser ranging are compared. The swing method is affected by waveform distortion.The least square method is widely used in curve fitting, which can effectively reduce the influence of waveform distortion and increase the accuracy by using higherorder fitting polynomials. The least square method uses all data to fit the curve; however, the polarization laser ranging algorithm focuses solely on the local minimum ranges. In terms of fitting efficiency and accuracy, it is not completely applicable to resolve the local minimum points of the demodulated signal. The moving least square (MLS) method is an optimization algorithm of the least square method that can simultaneously realize interval fitting and highprecision fitting near special points. This is suitable for highprecision fitting using the local minimum range data. In this study, a polarizationranging algorithm based on the improved moving least square (IMLS) algorithm is proposed. The algorithm flow is as follows. First, the algorithm achieves global fit and determines the intervals containing the minimum points. Second, it performs curve fitting using the MLS algorithm along the curve in one of the intervals until it finds the minimum point in this interval. Then, the influence radius is selected automatically according to the mean square deviation, and the frequency corresponding to the local minimum point is calculated. Finally, the ...