In this study, a novel least-squares-based method is proposed to measure the distance using a triangular-wave amplitude modulation laser. Further, we designed two channels comprising a reference signal and a measured signal that exhibit an optical path difference. Their return signals were fitted using the improved least-squares-based straight-line fitting algorithm, and a series of fitting parameters and singular characteristic points were obtained for the triangular-wave. Subsequently, we estimated the detection distance using the proposed theoretical algorithm based on the relation of the time shift information associated with the characteristic points of two signals. The average measurement error associated with this laser ranging system is 3.2 mm at a 10-m measurement range in case of a triangular-wave modulation frequency of 10 kHz, demonstrating the reliability of the proposed method. Furthermore, the proposed method exhibits certain application potential with respect to short-scale laser ranging.