This paper studied B (biomass of aquatic vascular plants) and N chemical compounds in two large-scale enclosures and one fence in East Lake of Wuhan from July,1993 to February,1995.B was highly negatively related to the concentration of NO 3-N in water.The concentration of TN in water obviously decreased when aquatic vascular plants grew well.The concentration of NO 3-N decrease was the major reason that leading to the decrease of TN concentration in water.Percentage of IN was obviously lower than that of ON.The concentration of IN was closely related to aquatic plants growth.The B in the enclosures was obviously higher than that in The control’s.The concentrations of NO 3-N,IN,and TN in the enclosures were obviously lower than those in the control’s.The concentrations of NH 4-N,NO 2-N and ON in the enclosures were not obviously different from thosein the control′s.