Abstract: Based on findings of soil investigation and growth of Phragmites australis in polders on Dongtan wetland of Chongming,discussions were held on how the soil environment factors subject to impact of fluctuating groundwater level affect growth of Phragmites australis.Results show that(1)groundwater level fluctuation varied in magnitude and time from quadrat to quadrat,resulting in different soil water regimes(P_1,2=0.004,P_1,3=0.001,P_2,3=0.040),which hence led to sharp variation of Phragmites australis in plant height and plant leaf-area,and the plants in the quadrat the highest in soil water content were found to be the tallest in plant height and the biggest in plant leaf-area;(2)soil total nitrogen content is significantly related to density and biomass,either above-or below-ground,of Phragmites australis.