Abstract: Nagqu serves as an important and demonstration center of Tibetan stockbreeding development located in an extremely harsh natural environment with vulnerable ecosystems.In recent years, large areas of alpine grassland ecosystems of Northern Tibet have severely degraded and have been threatened by soil erosion, desertification, and human activities. The annual variation of vegetation is influenced by both natural conditions and human disturbances. To efficiently solve the complex resource-related and environmental issues, it is necessary to clarify how human factors affect the normal growth of rangeland vegetation. Various statistical analyses and time-series NDVI (normalized difference vegetation index) datasets from MODIS sensors between 2000 and 2009, were used to monitor the spatio-temporal variation of grassland. The relationships between grassland degradation and various human factors are discussed based on qualitative and quantitative systematic analysis. 1) Due to snow melting related to global warming, the vegetation in some desertified and snow-covered regions of high altitude mountains showed an actively recovering trend, while the grasslands in purely livestock-breeding counties (such as Nagqu, Amdo and Nyainrong) of central Nagqu had some degenerative phenomenon; 2) The spatial patterns of density maps of residential distribution and road network, vegetation NDVI image, and yearly variation map of vegetation NDVI showed similar spatial clustering characters, indicating that human activities directly influenced growth and reproduction of plants in flourishing vegetation cover; 3) Taking Nagqu town and state highway No. 109 as typical instances of human factors, the vegetation in regions closer to town centers or the road axis with more intense human disturbances showed more severe degradation. Further statistical analyses showed a linear upward trend for population, numbers of livestock and traffic-construction projects in Nagqu, which will bring serious threats to sustainable development of local pastures; 4) Additionally, the grassland in Nagqu was also destroyed by grinding of tourists’ and herders’ vehicles, mining, digging herbal medicine, house-construction projects for low-income residents, and mice disasters. In order to protect the healthy development of Nagqu’s rangelands and local economy, several feasible and constructive measures are proposed.