An expansive alpine grassland ecosystem dominates the landscape in Northern Tibet, and the status of this grassland has significant implications for the major Asian rivers, and for the climate and eco-environment of Tibet and the wider region. The harsh natural environment and fragile ecosystem, together with increasing frequency and intensity of human activities such as pastoralism, and climate change, have resulted in increasing reports of degradation of the grassland ecosystem. We used vegetation cover as main indicator of ecosystem health, and with remote sensing monitoring, calculated the grassland degradation index (GDI) and evaluated grassland degradation in Northern Tibet from 2000 to 2010. The analysis was based on the Normalized Differential Vegetation Index (NDVI) data from the Advanced Very High-Resolution Radiometer (AVHRR) with a spatial resolution of 8 km from 1981 to 1985 and from Moderate Resolution Imaging Spectroradiometer (MODIS) with a spatial resolution of 0.25 km of 2000-2010. Then, we have analyzed the temporal and spatial distribution of grassland degradation in Northern Tibet from 2000 to 2010. It was found that grassland degradation in Northern Tibet was still severe. The GDI was 1.97 in 2010, near to seriously degraded status. The extremely seriously degraded and seriously degraded categories occupied 6.5% and 19.0% of the study area, respectively. The moderately and slightly degraded grassland categories accounted for 15.1% and 12.1%, respectively. Undegraded grassland occupied 41.8% of the total grassland area in 2010. The extent of extremely seriously degraded and seriously degraded categories was greatly increased in the data from 2000-2010, compared with the period from 1981-1985. However, the increase in grassland degradation in Northern Tibet from 2000 to 2010 was slight, with the mean value of the GDI being 1.84 in 2010, representing a change from light degradation to moderate degradation in Northern Tibet from 2000 to 2010.