Abstract: The global warming situation has intensified, and greenhouse gas emissions are one of the key factors. Carbon dioxide, as the main greenhouse gas (GHG), requires high-precision monitoring technology as the basis for GHG tracking. On this basis, monitoring the carbon dioxide isotope composition not only enables high-precision concentration monitoring but also allows for distinguishing the contributions of different emission sources to the carbon cycle process, achieving the tracking and traceability of anthropogenic and natural emissions. Developing high-precision carbon dioxide isotope monitoring technology is of great significance for improving the accuracy of carbon emission inventories and optimizing carbon emission reduction measures. In nature, carbon isotope gas concentrations are usually on the order of 10⁻⁶ of atmospheric concentrations and are affected by measurement conditions, which leads to increased difficulty in carbon isotope measurements. This paper reviews the research progress of infrared absorption spectroscopy techniques for measuring carbon dioxide stable isotope concentrations, analyzes the principles and research progress of high-sensitivity frequency-stabilized cavity ring-down spectroscopy (FS-CRDS), and provides an outlook on the future direction of stable isotope spectroscopy research. As an emerging optical detection technology, FS-CRDS overcomes the shortcomings of traditional methods, such as insufficient measurement accuracy and low sensitivity, and may become a new generation of standard methods for measuring GHGs and isotope abundance.