Comparative studies were carried out to study the distribution, species and life-forms composition of Ottelia acuminata communities over the past three decades.Results showed that in comparison to year 1980:1) Ottelia acuminata communities are only found in Lake Luguhu and Lake Jianhu nowadays.2) Species composition has been changed, e.g.the total number of species in Lake Luguhu increased from 7 to 10 during 1980 and 2008.Similarly, the total number of species in Lake Jianhu increased from 6 to 12 during 1980 and 2011.3) Life-forms composition has become more complex.The submerged-floating life-form system has developed to a submerged-floating-leaved-floating life-form system in Lake Luguhu, whereas the submerged life-form system has developed to a submerged-floating-leaved-floating-hygrophyte life-form system in Lake Jianhu.4) The replacement of species occurred at the level of family, genus and species, and the changes in Lake Jianhu were dramatic.By contrast, there were no much changes in Lake Luguhu.