【Objective】Paddy soil is a type of anthropogenic soil formed through long-term water cultivation and ripening, which has a high organic carbon storage and carbon sequestration potential. Clarifying the protection mechanisms of organic carbon in paddy soil can provide a theoretical basis for carbon sequestration, emission reduction, and sustainable utilization of paddy soil. 【Method】Using a 1000-year chronosequence of paddy soils formed through coastal reclamation in Eastern China, we investigated the distribution characteristics and evolution patterns of occluded/free and particulate/mineral-bound organic carbon within soil aggregates under long-term rice cultivation. This was achieved through methods such as force-stable aggregate fractionation and physical particle/density grouping. 【Result】While soil organic carbon (SOC) gradually accumulated under long-term rice cultivation, the contents of particulate organic carbon (POC) and mineral-bound organic carbon (MOC) also increased. However, MOC was the dominant form, accounting for 64.40%~87.89% of the total SOC pool. The distribution patterns of different size soil aggregates were consistent, with macroaggregates (74.0%~77.6%) being the most abundant, followed by microaggregates (9.2%~15.9%) and silt and clay-sized microaggregates (8.6%~15.7%). Therefore, over 70.00% of SOC was stored in the macroaggregates. The organic carbon content of aggregates of all particle sizes increased with the increase of paddy cultivation age and grain size, which were 7.39~13.78 g·kg-1, 1.72~2.74 g·kg-1 and 0.66~1.92 g·kg-1. Among different types of soil aggregates, mineral-bound organic carbon (MOC) was the dominant form. In macroaggregates, occluded microaggregates, and free microaggregates, the MOC contents were up to 2.9, 1.1, and 3.2 times higher than POC, respectively. The protective effect of occluded microaggregates on POC was stronger than free microaggregates, with the POC content in occluded microaggregates being up to 1.5 times higher than in free microaggregates. 【Conclusion】Long-term rice cultivation is beneficial for SOC sequestration under the physical protection of soil aggregates. The protective effect of occluded microaggregates on POC is a potential mechanism for carbon sequestration in paddy soil.