As one of the largest wetland distributed regions in China, The Sanjiang Plain is a globally significant hotspot for wetland biodiversity conservation. However, during the past fifty years, it experienced extensive wetlands loss and degradation, which has directly threatened the regional biodiversity. While knowledge of the structure and function of local wetlands remains poor. In order to protect wetland and its biodiversity more effectively, there is clearly a need for information of basic wetland structure and function. It is, however, evident from the literature on Sanjiang Plain wetlands that there were no attempts to explore plant community composition and diversity along environment gradient in local wetland. Honghe National Nature Reserve(HNNR),an epitome of the Sanjiang Plain, has been selected to carry out this study to increase these understandings. This study confirmed two typical wetland, the floodplain wetland and the circled depression .Within each typical wetland, Five communities from central marsh to peripheral island forest wetland were distinctly identified along the environmental gradient. The analysis results from aforesaid gradients showed: (1) there exist visible changes in the community composite, including the constructive species and dominant species, companion species and their dominance, and bryophyte species of each community; (2)the species richness gradually increases, the index is 26、41、51、68 and 82 respectively; (3)Alpha diversity has a different fashion compared with species richness. the evenness and Shannon-Winner diversity has a distribution of irregularly “N” shape .while the dominance has opposite trend, two exceptional communities are marsh meadow community and wet meadow community; (4)β diversity gradually decreases and then increases ,the low apex value for Jaccard index and Cody index is between marsh meadow and wet meadow, the high apex value is between bush meadow and island forest wetland. The research concludes that: the change of community composite and species richness is primarily dominated by the change of habitats; the pattern of Alpha diversity is mainly determined by the habitat and the biologic characters of dominant species; the change of β diversity is correlated with many factors, The specific reason deserve deep researches.