【Objective】 Protection of particulate organic matter (POM)within soil aggregates has been recognized to be one of the principal mechanisms of C sequestration in soil. The low soil organic carbon (SOC) content of Shajiang black soil is a major factor for limiting crop yields in the Huaibei plain. Increasing SOC sequestration by returning crop residues to the field has been recommended. No-tillage (NT), rotary tillage (RT), and deep tillage (DT) with straw return (S) are commonly implemented. The objective of this study was to evaluate the spatial distribution of POM within aggregates in Shajiang black soil under various straw return practices. 【Method】 The six-year field experiment was conducted using X-ray CT technology and machine learning. The soil aggregates (6-8 mm in diameter) were collected from depths of 0-10, 10-20, and 20-40 cm. POM is divided into two parts: fresh residue and old POM, based on its morphological characteristics. 【Results】Overall, the POM within aggregates was primarily composed of fresh residues, comprising 76.4% to 87.0% across various soil layers under three different straw return practices. The distribution ratio of fresh residues in connected pores ranged from 0.266 to 0.788, while the distribution ratio of old POM varied between 0.177 and 0.569. There was a substantial quantity of POM was distributed within aggregates under NTS treatment in the 0-10 cm soil layer. Fresh residues and old POM were primarily distributed in the connected pores, with the proportions of 0.788 and 0.569, respectively. In the 20-40 cm soil layer, POM volume density within aggregates was highest under DPS treatment among all the treatments. Specifically, the proportions of fresh residue and aged POM distributed in the connected pores were 0.729 and 0.536, respectively. In comparison to the RTS treatment, the NTS led to a significant change in both the total POM volume density and fresh residue volume density by 54.4% and 56.7% within the 0-10 cm soil layer (P < 0.05), respectively. Additionally, the NTS treatment resulted in a 25.5% increase in the proportion of fresh residues in connected pores and a remarkable 96.4% increase in its volume density (P < 0.05). Furthermore, the DPS treatment resulted in a reduction of 37.4% in total POM and 40.4% in fresh residue volume density within the 0-10 cm soil layer (P < 0.05). However, there were no significant differences observed in the total POM volume density, porosity (>16 μm), or connected porosity of the aggregates among the NTS, RTS and DPS treatments within the 10-20 cm soil layer (P > 0.05). Compared with the RTS, the DPS treatment led to a significant increase in the total POM volume density by 2.78 times within the 20-40 cm soil layer, with the fresh residue and old POM volume density increasing by 3.10 and 1.72 times (P < 0.05), respectively. Additionally, the DPS treatment significantly increased the porosity of aggregates (>16 μm) and connected porosity by 74.2% and 142.8% within the 20-40 cm soil layer (P < 0.05), while it increased the fresh residue volume density and old POM volume density in the connected pores by 9.41 times and 7.96 times (P < 0.05), respectively. 【Conclusion】 The substantial increase in POM volume density within aggregates primarily stems from a significant rise in fresh residue volume density observed in the topsoil (0-10 cm)under no-tillage, as well as in the deeper soil (20-40 cm)following deep ploughing with straw incorporation. Connected pores serve as pivotal reservoirs for the storage and transformation of fresh residue through decomposition processes. Our findings suggest that deep tillage promotes the formation of connected pores and POM accumulation in the deeper soil layers, which is significant for improving agricultural soil quality and soil carbon sequestration in Shajiang black soil.