Abstract: Based on scientific exploration in 1983 and 2013, the data of wetland vegetation were collected and analyzed. In the last 30 years, aquatic vegetations of Poyang Lake were in a slowly degenerative process, the conclusion shown that: (1) compared with the 1983, the area of submersed aquatic vegetations in 2013 were decreased significantly, submersed aquatic vegetations were decreased by 37.72%, water caltrop was decreased by 87.6%; (2) community structure was simplified, community species were decreased from 5-8 to 3-5, dominant species were changed from Potamogeton wrightii Morong to Vallisneria sp.; (3)the biodiversity and biomass in unit area was decreased. The main reasons for the degeneration were following as: (1) long duration of low water lever reduced the living space for aquatic vegetations; (2) habitat of submerged aquatic vegetation were deteriorated by increasing concentration of nitrogen and phosphorus; (3) growing of submerged aquatic vegetation were disturbed by flood, flood might as a turning point for succession of submerged aquatic vegetation; (4) submerged aquatic vegetation were influenced by human reactivity. To contain the degenerative evolution and maintain the health of wetland vegetation ecosystem, human activities should be controlled, making Poyang Lake to be rehabilitated.