In view of management the carbon sink of grassland ecosystem on Sanjiangyuan regions, Qinghai-Tibetan Plateau, this study analyzes the causes of carbon loss in the areas. Overgrazing is the main cause of grassland carbon losses, while climate change and soil nutrition have no significant effects. Moderate grazing and higher species diversity will benefit grassland carbon sequestration. Based on these analyses, we ensure principles of managing grassland carbon sink : Take Half Leave Half for natural grasslands, Maintain Original Add Diversity" for lightly and moderate degraded grasslands, and Categorical Management" for Black Soil Beech" degraded grasslands. Government initiated eco-engineers, such as restoring degraded grasslands and grain for green, could improve ecosystem carbon sequestration, previously it emitted into the atmosphere. It will improve forage utilization efficiency and reduce carbon emissions per unit animal products by changing the traditional livestock production which only relies on natural grasslands to the Warm Season Grazing and Cold Season Feedlot" , a new approach of grassland livestock production system to reduce carbon emission. In order to maintain and enhance the carbon sink function of alpine grasslands on the Sanjiangyuan regions, it is an urgent need to use natural grasslands rationally, restoring degraded grassland with high species diversity, constructing fodder production bases with high-quality and extending the new livestock production system.