The middle and lower Wuyuer River in Songnen Plain is one of the concentrative and extensive distribution areas of inland wetlands in Northeast China.Located between 45°53.3'～48°3.06'N and 122°59.3'～125°42.1'E,it covers an area of 2.53×106ha.Wetlands in this region perform important natural functions in improving water quality,providing flood control,maintaining environment and assisting groundwater recharge.The vast expanse of marshes and numerous lakes and ponds constitute a remarkable natural heritage and serve as an important wintering site for migratory birds.In the past several decades,land cover in the region underwent dramatic changes and the progressive loss and conversion of wetlands has become a key conservation issue.Based on Landsat MSS,TM/ETM imagery and GIS technology,using the theory and methods of landscape ecology,the landscape change of wetlands in the middle and lower Wuyuer River since the mid 1970s was analyzed.The results showed that area of marsh decreased from 39.51×104 ha to 32.04×104ha,while the area of cropland increased 12.97×104ha during 1976-2000.About 5.58×104ha and 3.40×104ha of marsh land were cultivated to dryland and paddy field individually,and 8.10×104ha of dryland were converted into paddy field.Due to shortage of water supply in the whole watershed,wetlands have dried up.About 8 097.7ha of marsh land were turned into dry grassland and 1 039.58ha degraded to saline-alkalined land.The loss of grassland was 16.93×104ha,of which 40% was opened up to cropland and 22.3% degraded into hardly-used land.The degenerated area of moderate coverage grassland reached 2.26×104ha,while low coverage grassland degenerated at a higher annual loss rate of 1.93%.The number and size of marsh patch decreased significantly and the shape of patch tended to be more irregular and complicated,which indicated that the wetland landscape became more fragmental.The loss and degradation of wetlands were closely related to warmer and drier regional climate.The study indicates that noticeable changes in wetland were resulted from climate fluctuation and intensive human activities including irrational reclamation,overgrazing,ditches drainage,road construction and so on.