This study used fractionation of aggregates and microaggregate-within-macroaggregate techniques to determine the organic carbon (C) content in aggregates and subfractions within aggregates of Mollisols after 11 years of continuous manuring in combination with mineral fertilizers. We aimed to explore the physical protection mechanisms of organic C stabilization of Mollisols at the soil aggregate level. The following four treatments were selected:OM0, only mineral fertilizers with no manure application; OM1, organic manure at the lowest level (7.5 Mg hm^-2 a^-1) plus mineral fertilizers; OM2, organic manure at the medium level (15 Mg hm^-2 a^-1) plus mineral fertilizers; and OM3, organic manure at the highest level (22.5 Mg hm^-2 a^-1) plus mineral fertilizers. Chemical fertilizers were applied at the same rate in each treatment. We found that organic manuring at various rates in combination with mineral fertilizers significantly enhanced the soil organic C (SOC) content. The SOC content in the OM1, OM2, and OM3-treated Mollisols was increased by 7.1%, 12.4%, and 15.7%, respectively, compared to that with OM0 treatment. Organic fertilization greatly facilitated the macroaggregation processes and enhanced the aggregate stability compared with OM0 treatment. The proportion of small macroaggregates (250-2000 μm) increased, whereas the proportion of the silt-plus-clay fraction decreased in response to an increase in the organic manure addition rates. However, there was no significant difference between the OM2 and OM3 treatments in the weight proportion of aggregates or their mean weight diameters. The turnover rate of macroaggregates increased with an increase in the application rates of organic manure. Organic manuring did not affect the C concentration of the silt-plus-clay fraction, which indicated that the silt and clay particles had approached or reached the C saturation level under the traditional management practices without organic manure input. An increase in the organic manure input slightly increased microaggregate C and significantly increased macroaggregate C. When organic manure was supplied at the highest level, microaggregate C did not change significantly, and only macroaggregate C continued to increase, which indicated that the microaggregate C pool had reached saturation and that additional C was sequestered in macroaggregates. Physical separation of the macroggregates into subfractions showed that the increase of organic C in macroaggregates was mainly attributable to the increase of coarse particulate organic matter in macroaggregates (coarse iPOM). These results suggested that C saturation occurred in a hierarchical fashion in a Mollisol. As the C input increased, the silt-plus-clay C pool saturated before the microaggregate C pool and, consequently, additional C input only accumulated in a relatively labile C pool, the coarse iPOM within macroaggregates, which has a relatively faster turnover rate.