A long-term field experiment has been carried out for 23 years in Jinxian County Institute of Red Soil in Jiangxi Province(116b20c24°E,28b15c30°N).One of the aims of the experiment is to study effects of longterm fertilization on labile organic carbon pool in soil aggregates in red paddy soil.It is designed to have the following treatments,i.e.1) Zero fert ilization(CK),2) chemical fert ilizers alone(NPK),3) organic fertilizers alone(OM),and 4) combinat ion of chemical and organic fertilizers(NPKM).Results show that content of labile organic carbon in soil aggregates decreased with soil depth.Long-term application of fertilizer,especially in Treatment NPKM,increased content of labile organic carbon in soil aggregates,thus preserving and improving quality of the soil carbon pool.Content of labile organic carbon and percentage of soil labile organic carbon to total soil organic carbon differed between aggregates different in size fraction.In terms of content of potent ial mineralization carbon(PMC) and percentage of PMC to total soil organic carbon,aggregate size fractions followed a decreasing order of 0.25~1 mm,1~3 mm,> 3 mm,0.05~0.25 mm,and < 0.05 mm,whereas in terms of percentage of content of dissolved organic carbon(DOC) to total soil organic carbon,they did a decreasing one of 0.05~0.25 mm,0.25~1 mm,1~3 mm,> 3 mm,and < 0.05 mm.Contents of PMC and DOC in aggregates were significantly related to content of SOC(p< 0.01) in A horizons of all treatments,and in soil P horizon as well,except for the size fraction of 1~3 mm(p< 0.05).Micro-aggregates(< 0.25 mm) was higher than macro-aggregates(> 0.25 mm) in stability.