To support targeted policy‑making for the Grain for Green Program (GFGP) in karst regions, taking Guangxi as an example, this study employs cropland utilization transfer matrices, ArcGIS spatial analysis, and centroid migration models to measure the spatial differentiation patterns and evolutionary characteristics of the carbon sequestration effects of the GFGP from 2000 to 2022. The results show that 1) carbon sequestration in project implementation areas increased significantly, with an average carbon sequestration increment of 393.92 gC/m². Spatially, it exhibited a dual-core agglomeration pattern of “central karst core area–southern coastal contiguous area”. The centroid of carbon sequestration shifted northward as the policy implementation gradually tilting towards ecologically fragile karst areas. 2) Carbon sequestration effects varied significantly among different GFGP conversion types. Conversion to shrubland emerged as the optimal pathway, with the highest average carbon sequestration increment of 483.74 gC/m². 3) Significant spatial differentiation in carbon sequestration effects existed between karst and non-karst areas. High-value carbon sequestration areas in non-karst regions were continuously distributed, while in karst regions, high-value areas were scattered and significantly constrained by site conditions. Shrub and grass restoration performed well in karst areas, whereas forest restoration exhibited a relatively weaker carbon sequestration effect due to geological limitations. Vegetation types for the GFGP should be configured according to local conditions, and differentiated management should be strengthened to enhance carbon sequestration benefits.