The Songnen Plain in Northeast China,one of the key national bases of agricultural production,went through remarkable land use/cover changes in recent years.This study aimed to explore the long-term land use/cover changes and the effects of these changes on the environment.The Landsat-based analysis showed that,during 1986-2000,cropland,built-up land and barren land had increased,among which cropland had the largest increase of 9,198km2 with an increase rate of 7.5%.Woodland,grassland,water body and swampland had decreased correspondingly,among which grassland had the most dramatic decrease of 6,127km2 with a decrease rate of 25.6%.The transition matrix results revealed that grassland,woodland and swampland were the three main land use types converted to cropland.Climate warming created the potential environment for the conversion of grassland and swampland into cropland.Land resources policy made by central and provincial governments of China affected the pattern and intensity of land use.Land use/cover changes accompanied by climatic variation brought out a series of environmental consequences,such as sand desertification of land,land salinization and alkalinization,grassland degradation,and more frequent floods.Under this circumstance,optimized land use structure and restoration measures are needed. The Songnen Plain in Northeast China, one of the key national bases of agricultural production, went through remarkable land use / cover changes in recent years. This study aimed to explore the long-term land use / cover changes and the effects of these changes on the environment. The Landsat-based analysis showed that, 1986-2000, cropland, built-up land and barren land had increased, among which cropland had the largest increase of 9,198km2 with an increase rate of 7.5% .Woodland, grassland, water body and swampland had decreased strongly, among which grassland had the most dramatic decrease of 6,127km2 with a decrease rate of 25.6%. transition matrix results revealed that grassland, woodland and swampland were the three main land use types converted to cropland .Climate warming created the potential environment for the conversion of grassland and swampland into cropland. Land resource policy made by central and provincial governments of China affected the pattern and intensity of land use.Land use / cover changes accompanied by climatic variation brought out a series of environmental consequences, such as sand desertification of land, land salinization and alkalinization, grassland degradation, and more frequent floods.Under this circumstance, optimized land use structure and restoration measures are needed.