In order to explore the relationship between the iron oxidates and soil organic matter in different size aggregates of paddy soil, based on analyzing the distribution patterns of iron oxidates in different treatments composed of N, P and K fertilizer and combined application of chemical fertilizer with green manure (Astragalus), rice straw and pig manure from a long-term experimental field. The results showed the phenomena of increasing Feo content (10.5%-58.5%) and Feo/Fed value (19%-76%), but decreasing Fed content (0.4%-13.8%) in bulk soil. The content of Feo in different size of fractions of soil decreased as the following order: 250-53 μm, < 53 μm, 2 000-250 μm, and Fed showed as: 250–53 μm, 2 000-250 μm, < 53 μm. However, the value of Feo/Fed decreased as the following one: <53 μm, 250-53 μm, 2 000-250 μm. The content of the SOC exhibited positive, negative and positive correlates with Feo, Fed, and Feo/Fed respectively. These results suggested that the activity of iron oxidates can be enhanced by SOC, and the pig manure combined with the N, P and K fertilizer treatment showed the maximum contents of Feo and Feo/Fed.