Grassland ecosystems play an important role in Chinese terrestrial ecosystems. However, great demand and excessive utilization of human beings on grassland resources have made it more susceptible to rapid degeneration in ecosystem properties and soil carbon levels. Among them, grazing is one of the key factors to make grassland ecosystems degraded. Therefore, it is very important to graze sustainably on grassland for preventing the degradation of grasslands. In this paper, as a case study, we simulated the potential changes of soil organic carbon (SOC) and net primary productivity (NPP) of meadow steppe dominated by Leymus chinensis under different grazing intensities based on CENTURY model (V4.0) in order to evaluate the effects of different grazing intensities and to pursue for optimal grazing intensity. The results showed that NPP and SOC of meadow steppe dominated by Leymus chinensis were very sensitive to grazing intensity. The optimal grazing intensity could be expressed by live shoots, and it should be less than 40% of whole live shoots per month, in order to mitigate the degradation of Leymus chinensis grassland and maintain its sustainable development. (C) 2008 Elsevier B.V. All rights reserved.