The contents and distribution characteristics of soluble organic nitrogen (SON) extracted with 1mol/L KCl from thesediments of six typical lakes including Lake Poyang, Lake Dongting in Hunan and Jiangxi Provinces were studied. The resultsindicated that the SON contents varied greatly from 17.18mg/kg to 292.31mg/kg (mean content,134.45mg/kg), comprising 51.86% oftotal soluble nitrogen (TSN) and 7.14% of total nitrogen (TN) in six lakes. The SON contents were significantly correlated with theircontents of TN and TSN, and SON were higher in the heavily polluted sediments than the light polluted ones. Their distributions ofSON were closely related to their lake pollution levels. The contents of free amino acid in the sediments were also studied, and theyvaried from 4.69 to 42.04mg/kg, comprising 18.80% of SON, and 1.24% of TN, and were significantly correlated with their SONcontents. The mean content of FAA was 23.27mg/kg, higher than those in soils in the same region. It indicated that there was morebioavailable SON from lake sediment than those from soil. The contents of SON in the sediments were also correlated with inorganicnitrogen, OM and CEC and so on. As one of the most important nitrogen compositions in lake sediments, SON should be paid moreattention to the nitrogen cycling and entrophication control in lakes.