Nitrogen plays a key role in lake eutrophication.We collected several undisturbed sediment corevS from two lakes, Lake Hongfeng and Lake Baihua in Guizhou Province to analyze the concentration and profile distributions of total, exchangeable inorganic and fixed nitrogen.The result's show that: (1) the nitrogen loctcl in the sediments of the two lakewS is higher in comparison with the average of lakes and reservoirs in China.Their average concentration of total nitrogen ranges from 0.36% to 0.40% Cdry sediment weight).It is obviously due to influence of diagenesis on vertical profile of total nitrogen in the sediment.The sediment of the reservoirs may be one of main nitrogen sources to cause the eutrophication.(2) The concentrations of total nitrogen and the burial environmental conditions are two main factors in distribution of the exchangeable nitrogen on sediment cores.(3) The fixed nitrogen is one of major sinks of nitrogen in the two reservoirs sediments.The concentration of fixed nitrogen in Lake Hongfeng and Lake Baihua, 434.05 mg/kg and 416.94mg/kg respectively, is higher than the data reported for others lakes or reservoirs of China.