There are serious land degradations caused by overgrazing in Qinghai-Tibet Plateau. Regional planning to preserve the plateau ecosystem is urgently needed. In this study, we develop a method to detect land degradations using time-series satellite images with a concept of resistance and resilience. A case study on plain field in Qinghai-Tibet plateau shows significant relationships between land degradation and topographical factors. In addition, the tendency of grazing activities had changed over the drought year. This knowledge will assist to predict the process of land degradations caused by grazing activity and prevent grazing activity to invade preserved area.