Abstract: Soil organic carbon (SOC) is a key participant in carbon cycling within ecosystems and a bearer of soil ecological functions.It plays a crucial role in maintaining regional ecological balance and sustainable land use.The ecosystem in karst areas is extremely fragile, and the soil organic carbon (SOC) content exhibits significant variability both horizontally and vertically, which limits the implementation of effective ecological protection and land management measures.This study focused on soils of three common land use types, including cultivated land, forest land, and grassland within the karst landform of Lujiang river basin.We analyzed the variations in SOC content across the 0~100 cm soil profiles and investigated the potential soil physicochemical properties that impacted SOC content.The results indicated: (1)SOC content decreased with an increasing soil depth under all land use types.The grassland and forest land consistently exhibited significantly higher SOC content than the cultivated land; (2)CaO, MgO, Total nitrogen (TN), pH, and alkaline nitrogen exhibited significant positive correlations with SOC content for all land use types, while SiO2 showed a significant negative correlation; (3) The random forest model further identified that CaO, and alkaline nitrogen were the key factors influencing SOC content.In summary, there was considerable variability in SOC content in the karst landscape, with grassland and forest land exhibited significantly higher SOC levels than cultivated land.CaO, and alkaline nitrogen were identified as crucial soil physicochemical indicators that affected SOC content