Abstract: To control the fertility of tobacco planting soil effectively and conduct carbon management in field reasonably,soil samples were collected from typical tobacco planting areas(Pengshui,Fengdu and Wushan) in Chongqing.The samples were divided into different soil aggregates by particle size with dry-sieve method,then the contents of high labile organic matter(HLOM),moderate labile organic matter(MLOM) and labile organic matter(LOM) in these aggregates were determined via treating the samples with KMnO₄ solution at the concentrations of 33,167 and 333 mmol·L^-1,respectively;and the distribution characteristics of organic matter and LOM in aggregates of each particle size range were analyzed.The results showed that:1) The major aggregates were the aggregates of 1-2 mm in particle size,which accounted for 40.16%-42.02% of total aggregates from the three areas.Except that the content of 0.25-0.5 mm aggregates was significantly higher in the samples from Wushan,there was no significant difference between the three areas(P>0.05).2) With the increase of particle size,the contents of total organic matter(TOM) and LOM decreased in all aggregates,while the contents of HLOM and MLOM decreased in the aggregates from Pengshui and Wushan,and decreased first then increased in the aggregates from Fengdu.3) TOM,HLOM,MLOM and LOM in soil mainly distributed in 1-2 mm aggregates,their percentage reached 29.99%-31.58%,24.29%-33.36%,24.15%-29.09% and 18.46%-21.69%,respectively.Therefore,1-2 mm aggregates were determined as the characteristic aggregates of organic matter for the typical tobacco planting soils in Chongqing.4) The contents of TOM and LOM in soils extremely significantly positively correlated to those in aggregates of<0.25 mm,respectively,it indicated that TOM and LOM in the aggregates of<0.25 mm could be used as a sensitive index for the change of organic matter content in tobacco planting soils in Chongqing.