Soil is an important component of the terrestrial ecosystem and plays a critical role in global carbon cycle. Better understanding the distribution pattern of soil carbon storage along environmental gradients will facilitate the projection of global change on terrestrial C cycling. This study was conducted to examine soil organic carbon and nitrogen contents in major grassland types along elevation gradients in the source region of Yangtze, Yellow and Lantsang Rivers. Soil organic carbon and nitrogen contents were greater at the highest (5 120 m a.s.l.) and lowest (4 176 m a.s.l.) sites and lower at middle site. Soil organic carbon and nitrogen contents increased with soil moisture along the altitudinal gradient. Partial correlation analysis showed that spatial variability of soil organic carbon and nitrogen contents at 0-30 cm soil layers could be primarily explain by soil moisture with partial correlation coefficients of 0.946 5、0.905 9 （p<0.01）, respectively. In addition, soil organic carbon and nitrogen contents showed positive linear correlations with plant cover and productivity and negative correlation trend with soil pH and total salt content.