College of Geo-exploration Science and Technology, Jilin University, Changchun 130026, China

Using landsat7,landsat5 and landsat8 remote sensing images, the changes of sandy and saline-alkali desertification of Tongyu County in 2000-2014 have been monitored. The results show that:�� The desertification degree in studied area was decreased. Although there exist a small number of local increases of desertification area, level and fragmentation, it shows an overall optimization and downward trend.�� The overall fragmentation index decreased from 4.57 km² to 5.46 km² during 2000-2007,and fell to 3.17 km² in 2014, indicating that the desertification is relatively scattered with poor connectivity in 2014,but more concentratedly distributed in 2007.�� The centroid displacement map illustrated that the centroid of each type of desertification in Tongyu County was moving to the northeast first and then to the south during the studied period.