In this study,Maduo county of Huashixia town in Qinghai Province was chosen as the typical plotting areas of alpine grassland in the source region of the Yellow River,Yangtze River and Lancangjiang River. Sampling plots were classified as 5 degradation levels,i.e. native,slightly degraded,moderately degraded,severely degraded and extremely severely degraded vegetation plots. Topsoil (0 ~ 30 cm)samples were separately collected in 10 cm-depth intervals. And we analyzed soil organic carbon contents and the composition of light and heavy fractions. Results showed that soil organic carbon and their fractions dramatically decreased as the degradation became more severe and soil depth got deeper. Compared to native vegetation,organic carbon contents at topsoil (0 ~ 30 cm) declined separately 19.4% at slightly degraded,44.4% at moderately degraded,67.0% at severely degraded and 79.7% at extremely severely degraded vegetation plots. Soil light fractions of organic carbon contents decreased 14.4% at slightly degraded,46.8% at moderately degraded,68.9% at severely degraded and 81.3% at extremely degraded vegetation plots. And soil heavy fractions of organic carbon content averagely decreased as 21.1% at slightly degraded,43.6% at moderately degraded,66.4% at severely degraded and 79.1% at extremely degraded vegetation plots. The proportions of soil light fraction organic carbon to organic carbon content ranged from 20.45% to 29.02%,and the those of soil heavy fraction organic carbon to organic carbon content varied as 70.98% ~ 79.55%. And soil organic carbon contents mainly distributed in the heavy fractions. In sum,topsoil soil organic carbon and its carbon fractions experienced dramatic decreases during the plantation degradation. As the alpine grassland degradation getting more severe,soil organic carbon contents decreased rapidly and lost severely. Therefore,the preservation of the alpine grassland is crucial for both ensuring the sustainability of animal husbandry in Qinghai province and the protection of terrestrial soil carbon stock of China in the future against the global warming challenge.