Abstract: The contents and distribution characteristics of dissolved organic nitrogen (DON) and free amino acids (FAA) from the 14 sediments of Lake Shankou, a typical mountain lake in northeast region were studied. The results indicated that the DON contents ranged from 124.41 to 560.17 mg/kg, averaged 304.78 mg/kg, comprising 45.25% of total dissolved nitrogen (TDN) and 5.27% of total nitrogen (TN) in Lake Shankou. The contents of FAA varied from 9.21 to 18.53 mg/kg (mean content, 12.19 mg/kg), comprising 4.35% of DON, 1.91% of TDN and 0.22% of TN, respectively. The DON molecular fraction results indicated that and low molecular weight DON and SUV254 with MW <1 ku about was the dominating fraction at the sampling stations, and high molecular weight DOC with MW >30 ku was the dominating fraction. The DOC/DON ratio results indicated that the small MW fractions(<1 ku) at station 2 which located at downstream of Lake Shankou derived from natural organic matters in sediments and allochthonous sources in water column, and the high MW fractions(>30 ku) at station 2 were mainly from external input in water. The DOC/DON ratios of the small MW fractions(<1 ku) and high MW fractions(>30 ku) at stations 8 and 13 were much low, implying their sources mainly from autochthonous contribution.