【Objective】In order to adequately meet the growing population"s demand for agricultural products, reducing the application of chemical fertilizers, investing in organic amendments, and improving the efficiency of nutrient use have been recognized as effective ways to guarantee food security. Different soil aggregate sizes exhibit significant variations in terms of water-heat conditions and nutrient distribution, which in turn influence nematode communities to varying extents. However, the impact of reduced chemical fertilizer application combined with different organic amendments on soil nematodes at the aggregate scale remain poorly understood. 【Method】This study investigated the interaction between reduced fertilizer application (2 levels: full chemical fertilizer NPK and 60% reduction in NPK) and organic amendment types (no organic amendment as control, straw, and biochar) in the red soil of dryland agriculture. Each treatment was further divided into four aggregate size classes (> 2 mm, 2-1 mm, 1-0.25 mm, < 0.25 mm). 【Result】The results indicated that the nematode abundance in all treatments with reduced fertilizer application was higher than that of the full chemical fertilizer treatment. Regardless of the fertilizer application, both straw and biochar significantly increased the total nematode abundance, and nematode numbers increased with the increase in aggregate size. Compared to straw application, biochar application generally decreased the abundance of bacterivorous nematodes while increasing the abundance of omnivorous nematodes. Notably, in the 2-1 mm aggregate size class, biochar addition decreased the abundance of bacterivorous and omnivorous nematodes compared to straw, but increased the abundance of fungivores nematodes. Nematode community analysis revealed that as aggregate size decreased, the nematode structure and enrichment indices tended to decrease, indicating greater environmental disturbance. Further analysis showed that, soil pH and moisture were key factors influencing nematode community structure at the larger aggregate scale, while soil organic carbon was the critical factor at the smaller aggregate scale (P<0.01). 【Conclusion】This study revealed that organic amendments, reduced fertilizer application, aggregate size, and their interactions significantly affected nematode communities. Therefore, the rational combination of organic amendment types and reduced fertilizer application should be considered to better protect soil health and guide agricultural production.