Vegetation is one of the important components of wetland, and vegetation biomass is a key indicator of the health status of the wetland ecosystem. Comphrehensive understanding of spatial distribution of vegetation biomass and its temporal variation is a pre-requirement for effective protection of bird habitats and scientific planning of wetland conservation. In this regard, it has been one of central topics in hydro-ecology, wetland ecology and vegetation ecology in past decades. In recent years, vegetation change has become one of major concerns with frequently occurred extreme droughts in the Poyang Lake National Nature Reserve (PLNRR) of China. To investigate the spaital changes of vegetation, MODIS (Moderate resolution Imaging Spectrordiometer) vegetation index products (MOD13Q1) were used to construct a model for retrieval of vegetation biomass with the coincident field data in PLNRR for the period from 2000-2011. GIS spatial analysis techniques were used to analyze the spatial patterns and seasonal variations of wetland vegetation biomass. Our findings can be summerizes as follows: (1) the power function best describe the relationship between MODIS-EVI (Enhanced Vegetation Index) and green yield of vegetaiton in PLNRR, with an overall accuracy of 91.7%. (2) Multi-year average of vegetation biomass displayed an island-like spatial pattern and can be classified into three zones. Vegetation biomass was lower than 285g/m², dominant with aquatic vegetation communities, for the bottom areas near the center of lakes. It ranged from 285 to 830 g/m², dominant with sedge communities, for the periphery of the lakes with an elevation of 14-15 m. The biomass was higher than 830 g/m² dominant with wormwood and reed communities, for surrounding delta or dyke areas with an elevation of 16-18 m. (3) Vegetation biomass showed different seasonal variations in each zone, which was jointly affected by multiple factors. Lake stage is the most important factor in regulating the spatial development of the vegetation biomass. Overall, the results should be not only helpful for understanding the change in biodiversity and ecosystem stability, but also provide a scientific basis for effective management and protection of wetland resources in the PLNRR.