Abstract: There was a sparse population in the Sanjiang Plain before the 19th century. At the beginning of the liberation, the farmland area was merely 78.6×10⁶ hm². So, the plain is famous for “the great northern wildness”. With the rapid increase of population and goverment investment, the farmland area had been 457.24×10⁴ hm² up to 1994. With reclamation over 40 years, the area of mire had decreased over 300×10⁴ hm², and the area of forest land decreased 307×10⁴ hm² by 1983, much more than that in 1949. Reclaiming and destorying forest and grass land has led to a series of ecological problems, such as the worse of soil erosion, the intrease of local desertification area and water erosion, the emphasis on reclamation rather than harness, the emphasis on use only rather than culture, the divorce between reclamation and construction, and result in the decrease at different level of cultivated soil fertility, and the intensification of pollution of farm chemicals, chemical fertilizer and surface water. In recent years, growing rice in large scale by well-irrigation has led to the falling of local ground water level. At the same time, it also has resulted in the destruction of biodiversity and the decrease of valuable and rare animals and plants. In order to restore and protect regional eco environment, it is imperative to stop reclaiming at once, take the way to reform middle and low yield cropland mainly, to strengthen effective management of mire nature reserves, to improve shelter-forest system, combine use with culture, culture soil, rational plan and use land. We should set up superior structure of agriculture forestry and stock raising, improve regional eco environment and reinforce sustainable use of regional resources.