Chemical composition and energy content of Elodea Nuttallii were determined by common methods of biochemical analysis. The digestibility, maximum consumption, protein efficiency ratio and food conversion coefficient of N. elodea by grass carp and Chinese bream were studied. In N. Elodea, water content amounted to 89.8%, protein, fat, cellulose and non-nitro-gen contents in dry matter were in proper orders:23.52%, 2.88%, 26.71%, 29.27%. Its protein contained 17 common amino acids, including 9 essential amino acid for fish. The content of amino alids was 198.04 mg/g(dry). Under mean water temperature 20.4℃, digestibilities of dry matter, protoin, fat, carbo-hydrates and amino acids in, grass carp fed N. Elodea were in proper order:56.02%, 73.9%, 58.46%, 77.00%, these in Chinese bream fed N. Eoldea were in proper order:54.97%, 72.96%, 64.63%, 51.36%, 77.00%. The maximum consumption (Y, g/24h) of grass carp fed N. Elodea was related to the body weight of fish (X, g) by equation Y=3.9449X^0.8357 (r=0.9154). In cage, protein efficiency and food conversion coefficient of N. Elodea by grass carp were in proper order:17.1%, 48.2. In enclosure, these of N. Elodea by grass carp were in proper orders:13.1% and 63.4%.