In shallow lakes.aquatic plants play very improtant roles in primary production and environ-mental protection.On the other hand.it can also cause silting-up by adding large amount of plant material to the lake bottom and release pollutant to the lake water when it dies and decays.The functions of aquatic plants car/be regulated reasonably by manipulating the structure and species composition of aquatic vegetation of the lake.In East Tathu Lake, more than 97% of the lake surface was covered by aquatic plants, which abso rbed 3916t nitrogen and 496t phophorous from the lake in a year to produce 1120325t plant biomass(fresh weight) About 599295t plant bio-amsswas harvested from thelaketo remove 198lt nitrogen and 296t phosphorous, equalto 28% of the external nitrogen load to remove 57% of the extecna1 phophorolls load of the Inke.There was stil1 521030t plant biomass remained and decayed in the lake which caused serious water Pollution and siliting-up of the lake basin Elodea Nuttallii was introd uced to the lake in 1986 and transplanted on a large scale in the past ten years.About 50000t of Elodea Nuttallii were har-vested as fish fod der in 1993 An experiment was carried out successfully to replace Zia lati in the 1ake with submerged plants.There alre still a lot to do to complete the task of reason-able regulation.