LDS is an advanced laser-based spectroscopic technique for gas sensing with a broad dynamic range and high immunity to optical power fluctuations. It has attracted considerable attention in trace gas detection and combustion diagnostics. Starting from the motivation for conducting research on LDS technology, this review systematically introduces the fundamental spectroscopic principles of LDS and establishes a theoretical analysis framework. It highlights the key features and implementation methods of HPSDS and CLaDS, and explores approaches for constructing calibration-free models. By examining the representative LDS applications in the past decade in typical scenarios such as combustion diagnostics, high-temperature flue gas monitoring, and environmental optical trace gas detection, this review elucidates the distinct technical requirements of these application domains. Finally, regarding such challenges as the insufficient detection sensitivity and complex system configurations, the paper indicates the future development directions from both fundamental research and practical application perspectives, providing a systematic reference for advancing the theoretical foundations and engineering applications of LDS.