In order to study the effects of cultivation and irrigation on soil aggregation and organic carbon, the study subjects were selected from the irrigation zone in Ningxia province, and selected the control and irrigated soil. Through the combination of dry and wet methods, we got the proportion of large macroaggregates (>2 mm), small macroaggregates (0.25~2 mm), microaggregates (0.25~0.053 mm) and silt + clay (<0.053 mm), and measured the content of organic carbon in each aggregate fraction and analyzed the relationship between organic carbon and total organic carbon. The results showed that aggregate distribution changed significantly (P<0.01) after irrigation, large macroaggregates and small macroaggregates proportion raised, microaggregates and silt + clay mass proportion decreased, the distribution trend was microaggregates>silt+clay>small macroaggregates>large macroaggregates. Irrigated soil aggregate stability was greater than that of the control soil, different types of irrigated soil had the same stability, and showed difference between control soils. In addition to <0.053 mm, the aggregate distribution of organic carbon after irrigation had significant difference (P<0.05), the organic carbon content had a "V" distribution with the size of the granule. Soil organic carbon in aggregate was higher in irrigated soil than that of the control soil, Irrigated-silted soil and Fluvo-aquic soil showed higher aggregate organic carbon content. There was a significant positive correlation between organic carbon in aggregate and total organic carbon in non-cultivated and non-irrigated natural soils, soil total organic carbon increase mainly depended on increment of >0.053 mm aggregate organic carbon. Cultivation and irrigation with sediment laden Yellow River water was significantly beneficial to increase the proportion of large scale aggregate, the stability of the aggregate, and the organic carbon content.