Two experiments in newly-culltivated slope land and upland with three treatments,Nil(CK),NPK(NPK),Straw NP(SNP),were selected to analyze the effects of ex situ rice straw incorporation on the distribution of organic carbon and nitrogen in water-stable macro-aggregates of hilly red soils.Results showed that,ex situ incorporation of straw increased water-stable macro-aggregates and the concentrations of organic carbon and nitrogen increased with increase of water-stable aggregate-size;ex situ incorporation of straw significantly increased the concentrations of organic carbon and nitrogen in water-stable macro-aggregates by 10.1%~78.5% and 9.4%~63.6%(p<0.05),and also increased the ratios of organic carbon and nitrogen in water-stable macro-aggregates(2~5 mm or 1~2 mm) to soil;Compared to inorganic fertilizer,ex situ incorporation of straw significantly increased the concentrations of organic carbon by 6.5%~46.1% in 0.5~1 mm,1~2 mm,2~5 mm,>5 mm water-stable aggregates and nitrogen by 8.7%~16.1% in 0.5~1 mm,1~2 mm,2~5 mm water-stable aggregates.Water-stable macro-aggregates have high potential to accumulate organic C and N,and ex situ incorporation of straw increased the concentrations and distributions of organic C and total N in water-stable macro-aggregates,which increased the ability of regulating soil fertility.Therefore,ex situ incorporation of straw was effective measure to improve soil structure,enhance and regulate soil fertility in hilly red soils.