During December 2002~December 2003, we sampled Phragmites communis distributed outside and inside of the seawall for four seasons in the Eastern End of Chongming Island, Shanghai. The research results indicated that Phragmites communis is dominant species of the local ecosystem. Its cover reaches to 70% and density is up to 211.83 shoots/m2 and biomass is over 1 783.8 g/m2. It is the main parts of elementary productivity in the area. After June 2003, the area was invaded by the Suaeda glauca and Zoysia japonica rapidly soon after the water of fish-ponds behind of the seawall was draught out, thus we analyze this succession of the biotic community with Principle Component Analysis (PCA) and demonstrate such a succession would be completed in a very short period and Suada glauca may replace Phragmites communis when the wetland become dry. Based on this results, we raise the recommendations on the wetland management in the coming restoration project in this area.