Different forms of water soluble nitrogen contents in surface sediment and contents of NO₃-N and NH₃-N in surface water from Longquan Lake, Sichuan Province were studied. Average contents of water soluble total nitrogen, water soluble NH₃-N and water soluble NO₃-N were 6.64 mg/kg, 1.22 mg/kg and 2.83 mg/kg in surface sediment, respectively. Average contents of NO₃-N and NH₃-N were 5.09 mg/L and 0.05 mg/L in surface water, respectively. The correlation of NO₃-N content between surface water and surface sediment was not significant, but NH₃-N content between surface water and surface sediment was significantly positively correlated, indicating that NH₃-N of surface water may be caused by NH₃-N released from surface sediment.