Aquatic vegetation and environment in Longgan Lake are investigated in September, 1993.The results show that the aquatic flora in the lake covers 26 families, 38 genus, 50 species.The distribution area is 283.5km²,making up 89.7% of the lake. Based on the domi-nent association combinations and structures, the following 9 association types can be cate-goried; (1) Zizania caduciflora ass.; (2) Nelumbo nucifera ass.; (3) Neiumbo nucifera-Trapa bicornis ass.; (4) Hydrilla verticillata+Vailtsneria spiralis+Ceratophyllum demersum ass.;(5) Hydrilla verticillata+Potamogeton maackianus ass.;(6) Vallisneria spiralis ass.; (7) Potamogeton malaiantis-Vallisneria spiralis ass.; (8) Trapa naians-Potamogeton mela-ianus+ Myriopkyllum spicatum-HydriUa verticillata ass.;(9) Potamogeton mcdaianus+Myriophyilum spkatum ass.After comparing the aquatic vegetation association types and their distribution in 1980 and 1993, the authors make some suggestions, i.e.: the annual 2147730t of aquatic vegetation should be exploited and utilized in a reasonable way; a net increase of 418L 8t/a in fishery potential may be reached when pen-fish-farming is widely populariged.