Abstract: 【Object】 This study investigated the effects of straw addition on organic carbon mineralization in soil aggregates under varying moisture conditions，aiming to elucidate the mechanisms underlying straw incorporation in soil organic carbon transformation and stabilization. 【Method】 Two types of soil（sandy and clay）were selected for the study. Using the wet sieving method，3 size fractions of aggregates（>0.25 mm，0.25-0.053 mm and <0.053 mm）were obtained. An indoor microcosm cultivation experiment was conducted with no straw added as a control，the differences in organic carbon mineralization characteristics of different particle-size aggregates were observed under straw addition and soil moisture settings as 40% and 60% of field water holding capacity（WHC）. 【Result】 Straw addition enhanced CO₂ emission rates and cumulative CO₂ release in both while soil and aggregates of all sizes，with cumulative CO₂ release in straw added treatments being as 1.2-1.7 times as that in controls without straw. Organic carbon mineralization rates and cumula‐tive mineralization were greater under 60% WHC compared to 40% WHC. Increasing moisture from 40% to 60% could elevate cumulative CO₂ release by an average of 15.2% in whole soil and 67.9% across aggregate sizes. Clay soil exhibited more pronounced responses，reaching a maximum cumulative CO₂ release of 3453.27 mg/kg. Furthermore，straw addition amplified the disparity in cumulative CO₂ release between 60% WHC and 40% WHC treatments in clay soil. Clay aggregates demonstrated stronger response to moisture and straw addition than sandy soil. Moreover ，the cumulative CO₂ release of different soil aggregates were different. In sandy soil，the order was >0.25 mm，0.25-0.053 mm，<0.053 mm， and whole soil. In clay soil，the order was >0.25 mm，<0.053 mm，0.25-0.053 mm，and whole soil. Partial least squares （PLS）structural equation model analysis identified straw addition，soil moisture content，and soil physical and chemical properties as key drivers of soil organic carbon mineralization，while aggregate size showed no significant effect on soil aggregate cumulative mineralization （P>0.05）. 【Conclusion】 Although differences in organic carbon mineralization among aggregate sizes are minimal，but exhibits strong responses to straw addition and moisture. High soil moisture content promotes the mineralization of organic carbon in soil aggregates，which is conducive to improving the carbon supply capacity of the soil.