Abstract: In order to research the effect of continuous straw returning on soil fertility and organic carbon distribution in aggregates under the conventional tillage of black soil, soil samples were collected from an 8-year field experiment carried out in black soil region of China, the effects of different treatments (no fertilizer-CK, chemical fertilizers-NPK, and chemical fertilizers plus straw returning-NPK+S) on soil nutrients and organic carbon content in water-stable aggregates were studied, and the initial soil sample in 2004 was regarded as the comparison. Results showed that, the 8-year continuous straw returning significantly increased the proportion of macro-aggregates (>0.25 mm) as compared with initial soil. In addition, the amount of macro-aggregates and mean weight diameter (MWD) of aggregates in the NPK+S treatment were significantly higher than those in the CK and NPK treatments. Compared with the initial soil sample, the content of soil organic matter (SOM) increased by 6.59% under the NPK+S treatment, whereas under the CK and NPK treatments, it decreased by 1.95 and 2.56%, respectively. After 8-year straw returning, the organic carbon contents in soil aggregate had a general increase, obviously higher than these in the CK and NPK treatments. Contributing rates of SOC of macro-aggregates in soil organic carbon had remarkably increased after 8-year straw returning whereas it was contrary for the micro-aggregates. Meanwhile, chemical fertilizers plus straw returning significantly increased the contents of alkali-hydrolyzed N, available P and available K. Compared with NPK, NPK+S had a more remarkable improvement for the soil available nutrients. Consequently, the application of chemical fertilizer plus straw returning could be prone to increase the stability and organic carbon content of soil aggregates, as well as improve the soil nutrient condition, so it had profound significance on enhancing black soil quality comprehensively.