The soils of long-term Chinese milk vetch-double cropping rice rotation in NanxianCounty，Hunan Province weretaken as the researchobject.When the fertilizer reduction was 20% and40%，and the return amount of Chinese milk vetchwas set at15，22.5，30，37. 5 t·hm -2，the effects of both reduced fertilizer and different returning amount of Chinese milk vetch on iron-manganese oxides in soil aggregates and their relationships with water stability of aggregates werestudied.The results showedthat:(1)Compared with thecontrol[alone returning of Chinese milkvetch(MV)and application of100% fertilizer(F)]，reducing the application of 20% and 40% of the chemical fertilizers combined with the applicationof Chinese milk vetch increased the content of >0.25 mm aggregates，reduced the content of <0.25 mm aggregates；thestability of aggregates increased by 8.91%～ 45.45% at 15 and 22.5 t·hm -2 Chinese milk vetch returning when reduced theapplication of chemicalfertilizers.(2)Compared with thecontrol，when the fertilizer was reduced by20%，the free ironand manganese content in the soil aggregates decreased with the increase of returning amount of Chinese milk vetch(15～ 30 t·hm-2).But the content of crystalline and complex iron and manganese significantly increased by 7.70%～ 72.31%and 10.75%～58.53%，respectively.(3)Correlation and path analysis showed that the stability of soil aggregates underchemical fertilizer reduction and Chinese milk vetch returning mainly depended on the iron oxide contents.While in iroNO_xides，amorphous and complex irons played a direct role in improving the stability of aggregates.