In order to investigate the carbon and nitrogen contents of aggregates and crop yield under long-term straw return in fluvo-aquic soil，with the wheat and maize rotation system as the study object，the characteristics of organic carbon and total nitrogen in soil water-stable aggregates and the yields of wheat and maize were studied using a 38-year located field experiment.Five treatments were set up，including no fertilizer control (CK)，straw return at rates of 0 kg/hm² (S0)，2250 kg/hm² (S2250)，4500 kg/hm² (S4500) and 9000 kg/hm² (S9000) combined with equal amounts of nitrogen and phosphorus fertilizers from the long-term field experiment.The results showed that the long-term fertilization and straw return increased the organic carbon and total nitrogen contents in soil water-stable aggregates，especially in 0～10 cm soil layer.With the increasing of straw amount，the improvement effect of the water-stable aggregates’ organic carbon was more obvious. But there was no significant difference on the carbon to nitrogen ratios in water-stable aggregates.The enrichment factors of organic carbon and total nitrogen in the >0.25 mm water-stabled aggregates were higher than those in other aggregates， and in 0～10 cm soil layer，S2250，S4500，and S9000 treatments all show a gradual decrease in the enrichment coefficient of organic carbon in aggregates as the particle size decreases.Also，the long-term fertilization and straw return increased the crop yields.The high amount of straw returning was more helpful to increase the yield of wheat.The crop yields increased linearly with the increase of organic carbon contents in the >0.25 mm water-stable aggregates.When the organic carbon contents in the >0.25 mm water-stabled aggregates increasing 1 g/kg，the wheat yields would increase 329.62 kg/hm².However，the wheat yield was little related with the organic carbon content in the aggregates of 0.25～0.053 and <0.053 mm. In conclusion，straw return could enhance soil fertility and increase crop yield.