<p>This study aims to understand the variation patterns, stability and influencing factors of soil organic carbon (SOC) and its fractions affected by different vegetation restoration years, and to clarify the driving mechanisms of the differences in vegetation restoration SOC in the urbanized karst areas. Four vegetation types (barren lands, forestlands, grasslands, shrublands) with restoration gradients of 1, 5, 10, 15, and 40 years were investigated. Undeveloped natural forests and 0-year bare land were set as references and initial controls, respectively, to analyze the effects of vegetation restoration on SOC content and its fractions. Shrublands exhibited stronger SOC accumulation than grasslands in the early restoration stage, while grasslands outperformed shrublands in the later stage, with barren lands showing the poorest accumulation. After 40 years of restoration, SOC contents in forestlands, grasslands and shrublands were 49.86%, 42.14% and 45.44% lower than those in undeveloped forests, respectively. SOC accumulation with restoration years was non-linear (initial increase - mid-term decrease - late-term increase). Vegetation type, restoration year, particulate organic carbon (POC) and soil inorganic carbon (SIC) were key factors affecting SOC, with POC (rather than mineral-associated organic carbon, MAOC) dominating urban SOC and driving its accumulation. The increase in the time after vegetation planting led to a rise in SOC concentration. Our research results were crucial for quantifying the SOC content affected by vegetation restoration and for better C management.</p>