Aims <p>Soil carbon (C) mineralization connects the soil C pool to atmospheric CO₂, and is governed by C substrate, microbial characteristics, and reactive oxygen species (ROS). Yet, how vegetation restoration modulated these drivers to regulate C mineralization across contrasting soil types remained unclear.</p> Methods <p>We selected croplands and adjacent grasslands and forestlands, both converted from croplands, on loess and sandy soil to investigate vegetation restoration effects on soil C mineralization, and to elucidate the roles of C substrate, microbial characteristics, and ROS.</p> Results <p>Vegetation restoration significantly increased soil C mineralization in both soil types, with the highest cumulative CO₂ efflux observed in forestland. This enhancement was driven by concurrent increases in microbial biomass, enzyme activity, C supply, and ROS concentrations. However, the dominant pathways diverged between soil types: C substrate supply predominated in loess soil, whereas microbial characteristics were primary in sandy soil. Notably, ROS explained more than 12% of the variance in C mineralization across both soil types. Furthermore, contrary to the conventional protective role of iron-bound organic C (Fe-OC), its accumulation following restoration indirectly facilitated C mineralization by enhancing C pools, microbial biomass, enzyme activity, and ROS generation, with this effect being more pronounced in fine-textured loess.</p> Conclusions <p>This study revealed a soil-type-dependent mechanism by which vegetation restoration drove soil C mineralization, highlighted the promoting roles of ROS and Fe-OC in this process, and provided a novel biogeochemical perspective for exploring soil C dynamics in restored ecosystems.</p>