Cavity ring-down spectroscopy (CRDS) technology has high precision, high sensitivity, and large linear dynamic range, and is widely used in environmental carbon and water cycle monitoring, human expiratory monitoring, and deep sea/ocean dissolved gas monitoring. This review article briefly introduces the basic principle of CRDS and its development history, and summarizes the recent progress in the application of trace gas and isotope detection in domestic and foreign research institutions. The content, the achieved progress, and the existing problems of our research are given in detail in the fields of environmental atmospheric greenhouse gas detection, Qinghai-Tibet Plateau gas profile detection, and deep-sea dissolved gases and their isotopes detection. Application prospect and future development trend of CRDS in trace gas detection are prospected.