Abstract: Field experiments investigating the effect of continuous lucerne (Medicago sativa) (L-L) and five rotation systems [lucerne-fallow (L-F), lucerne-wheat (L-W), lucerne-corn (L-C), lucerne-potato (L-P), lucerne-millet (L-M)] on total organic carbon (TOC), readily oxidation organic carbon (ROC), light fraction organic carbon (LFOC) and heavy fraction organic carbon (HFOC) in a typical arid area of the Western Loess Plateau. The results showed that under different rotation systems TOC and soil organic carbon fractions decreased with increasing soil depth (0-200 cm soil depth). The highest TOC, ROC and HFOC values were found in the surface soil layer (0-5 cm) under the L-L rotation system, and the lowest values at mid depths (30-50 cm) under the L-W rotation system. The highest and lowest values for LFOC were found in the surface soil layer (0-5 cm) under the L-P rotation and the bottom soil layer (170-200 cm) under the L-C rotation, respectively. Compared with L-L rotation, the L-W, L-C, L-P and L-M rotations reduced TOC by 17.4%, 9.3%, 18.4% and 9.3%, respectively. Similarly, ROC was reduced by 28.1%, 8.5%, 28.1% and 23.2% and HFOC by 18.8%, 10.1%, 20.5% and 12.5% respectively. However, LFOC increased by 7.4%, 5.3%, 22.2% and 57.4% under L-W, L-C, L-P and L-M rotations, respectively. It was concluded that lucerne-grain rotation systems reduce TOC.