Abstract: The accumulation and leaching of soil inorganic carbon (SIC) play crucial roles in the global carbon balance and represent a key research focus in carbon cycling studies. Accurate quantification of SIC content and its stable isotope ratio is critical for identifying the current "missing" carbon sink in terrestrial ecosystems. This study developed a rapid, high-throughput method for synchronous measurement of soil inorganic carbon (IC) content and its carbon isotope ratios using cavity ring-down spectroscopy(CRDS) combined with an automated small-volume gas sampler. A synchronous analysis method for inorganic carbon content and isotope ratios in different types of soils was established by analyzing certified reference materials. Results demonstrated that this method has a measurement range of 0.050−0.500 mg (as carbonate), with a correlation coefficient ≥0.999. The accuracy of SIC analysis was better than 1 g/kg, and the accuracy of carbon isotope analysis was better than 0.5 ‰, with no observed isotope fractionation. The newly developed method was applied to determine inorganic carbon content and isotope ratios in soils with different types and SIC contents. The results showed that all samples achieved good repeatability, and the results were consistent with those measured using the original method. Moreover, the accuracy of SIC content and isotope ratios in soils of 100 mesh is better than that in soils of 60 mesh. The optimized method is simple to operate, offers a low detection limit, requires minimal processing time, and exhibits excellent repeatability, making it highly suitable for rapid and batch analysis of SIC content and its stable carbon isotope ratio.