Revegetation of degraded arable land with perennial legumes in semiarid areas of China is expected to increase soil carbon sequestration. In this study we assessed the effect of alfalfa, bush clover and milk vetch on the SOC concentration and SOC stock accumulated annually over a 2 m soil profile. The results indicated that conversion of arable land to perennial legume pasture resulted in a significant increase in SOC, particularly at soil depths below 1 m.