Arid and semi-arid saline-alkali soils constitute a previously unquantified inorganic carbon sink that can account for a substantial portion of the residual terrestrial CO2 budget. To exploit the productive potential of saline-alkali lands along the Yellow River, this study considers the alkalinity (pH), salinity (EC), and soil inorganic carbon (SIC) at the Hangjing-hou Banner region, in the Inner Mongolia section of the Yellow River. Using geographic information system technology, a spatial analysis of pH, EC, and SIC in saline-alkali soil before summer irrigation was conducted. The 3D Copula joint distribution model were applied to quantitatively investigate the coupling relationships among pH, EC, and SIC. Alkaliza-tion is predominantly moderate (0-40 cm), salinization is mainly non-salinized, and SIC is highly concentrated (15-20 g/kg) across both layers (0-40 cm). Within a depth of 140 cm, the probability of cultivable land being slightly alkaline and mildly salinized or lower ranges is 30.16%, while the probability of these zones being suitable for inorganic carbon sequestration reaches 69.84%. Within the depth range of 140 cm, an empirical pH (8.0-8.8) and EC (1.5-2.5 ms/cm) range for high SIC (> 19 g/kg) was identifie