By using the method of space-for-timereplacement，we analyzed the evolution characteristics of soil organiccarbon(SOC)and its fractions(active carbon and passivecarbon)within soil aggregates during the walnut planting processfor providing scientific basis for sustainable development of walnut orchards inChina.Three walnut plantations of differentages(7，14 and 21years)and the adjacent wasteland without walnut planting were selected as the research objects in the walnut demonstration base of Hebei Lvling Fruit IndustryCo.，Ltd.By using the optimal-moisture sieving method and modified Walkley-Blackmethod，we analyzed the differences in soil aggregate distribution and aggregate-associated SOC and its fractions acrosswalnut orchards with different plantingyears.Results showedthat:(1)The proportions of >2 and <0.25 mm aggregates in the surfacesoil(0-40cm)were increased and declined with increasing walnut plantationages，respectively，which caused the values of mean weightdiameter(MWD)was increased with increasing walnut plantationages(increased by 2.3%-18.2%).Meanwhile，the values of MWD within aggregates in the 0-20 layer were significantly higher than those in the 20-40 and 40-60 cmlayers.(2)As the walnut plantation agesincreased，the contents of SOC(both active carbon and passivecarbon)and total nitrogen as well asSOC activity of the largeraggregates(>2 and 2-0.25mm)in the surfacesoils increasedbasically.However，the SOCcontents，SOC activity and total nitrogen in the deep soil(40-60cm)and <0.25 mm aggregates were not sensitive towalnut plantationages.(3)TheSOC(i.e.，active carbon and passivecarbon)，total nitrogencontents，carbon nitrogenratio(C/N)values and SOC activity showed decreasing trendswith aggregate size decreased. Meanwhile，these indices decreased gradually with anincrease in soildepths.Inconclusion， long-term walnutplantations(>14 years)could increase soil aggregate stability and were beneficial for SOC accumulationand the improvement of SOC activity within largeraggregates；however，these indices within <0.25 mm aggregates and deep soils were difficultly influenced by walnut plantation ages.