Abstract: The desertified lands in Songnen plain are distributed mainly in the center and west of the plain, including the Songnen desert land and a part of Horqin desert land. The desertification is located in the semiarid area, where the annual precipitation is 350-450 mm, with sensitive ecologic environment. The desertification of Songnen plain in both 1986 and 2001 are interpreted by RS and GIS technique. Combined with field investigation, the current situation and changing trend of the desertification is studied. The result reveals that the desertification in Songnen plain is in a developing trend. From 1986 to 2001, the area of desertified land increased 861.1 km², in an expanding rate of 0.44% annually. The heavily desertified land changed in the greatest expanding rate. The area of moderate desertified land increased the most; while that of the lightly desertified land decreased a little.