Abstract:【Objective】 Soil inorganic carbon (SIC) plays a crucial role in soil ecosystem functions and carbon cycling processes. While the dynamics of soil organic carbon have been extensively studied, the long-term evolution of SIC in coastal regions remains poorly understood.【Method】 This study focused on soil calcium carbonate in coastal regions. By establishing a millennial soil chronosequence, we determined the calcium carbonate stock at different soil depths and soil ages to investigate the evolution of soil inorganic carbon in coastal areas. 【Result】 SIC stock was higher within the 20~100 cm soil layer and lower in the surface soil layer (0~20 cm). A significant positive linear relationship was observed between SIC stock in the 0~50 cm layer and that in the entire 1 m soil profile (R2 = 0.904, P < 0.01), indicating that SIC stock in the 0~50 cm layer can be used to approximate the total SIC storage in the 1 m profile in the study area. This provides a reference for SIC stock assessments in similar coastal reclaimed areas. The SIC stock showed a negative correlation with soil age, meaning it decreased significantly as soil age increased. Also, the rate of SIC leaching decreased significantly with both increasing soil age and greater soil depth. 【Conclusion】 This study provides novel insights for estimating regional inorganic carbon storage and elucidating the leaching dynamics of inorganic carbon during pedogenesis, offering a scientific basis for refining carbon cycle models, predicting terrestrial carbon sink potential, and formulating evidence-based management strategies.