Using Landsat TM and ETM + images from 1984 to 2004, this paper analyzed the hydrology, soil, plant condition of the Widgeon Lake Wetland in Beijing. And the results are as follows: Salinized area had increased every year and reached to a head in 2004. Due to the soil salinization, the marsh vegetation species changed to the mesophytic, xeromorphic and salt tolerable ones. Along with the continuously shrinking of water area, wetland dominated the low coverage. The cold-humid effect of wetland had been impaired for the breakage of wetland environment in recent years. The decrease amount of regional daily evapotranspiration proved that the climate was drying and warming. The regional ecological negative effects were closely connected with the decrease of wetland resources. We should bring forward corresponding effective protection and utilization measures and give the scientific basis for the restoration of wetland resources.