Experiments on oenanthe javanicas planted in floating-beds were conducted to study distribution of biomass and absorbing contents of N and P from eutrophic water body. The average fresh weight was 35.22 g per plant, with the above-water part counted 77% and the under-water part 23%. The waterborne part played a key role in the biomass structure. The directly absorbing contents of N and P were 13.05-33.14 kg/(hm2·a) and ?5.62-6.67 kg/(hm2·a), respectively. The results showed that the oenanthe javanica grows well under the lower temperature and is good for water purification on the eutrophic water body.