The increasing rate of sandy desertification lands in Zoige County has been regarded as an imminent threat recently. There is an urgent need to monitor the status, trend of desertification. This study used a land cover classification process of integrating Support Vector Machine classifier (SVM) with threshold method to extract the sandy lands based on Landsat data collected from 1990 to 2017. Furthermore, we quantitatively analyzed the evolution trend of the grassland desertification and verified the effect of desertification control using the unmanned aerial vehicle (UAV) image acquired in 2019. Three conclusions are drawn from the study. First, the sandy land is mainly distributed along the directions of prevailing wind at the edges of mountains in the southwest. Second, the area of sandy lands increased from 29.75 km² in 1990 to 46.87 km² in 2005 and then decreased to 22.58 km² in 2013. While during 2014-2017, the area increased to 33.61 km². Third, the increasing of sandy lands is closely related to the terrain and water resources distribution. Ecological restoration policies, especially the ecological recovery projects implemented are the main driving factor of desertification reversion. The results of this study can provide effective data and decision support for combating desertification.