Abstract: By means of random amplified polymorphic DNA markers, a molecular ecological study was made with Sabina vulgaris populations at 4 succession stages in Maowusu sandy grassland, aimed to reveal the relationships between molecular variation and succession stages. A total of 17 random primers were selected for amplification, and 190 repetitive loci were produced, of which, 173 were polymorphic. The data were analyzed by POPGENE 3.2 Version 1.31. The results showed that the genetic diversity of S. vulgarispopulations was high, and changed with succession stages. The percentage of polymorphic loci in each S. vulgaris population ranged from 64.21% to 74.63%, with the highest in early succession stage Artemisia ordosica+S. vulgaris on semi-fixed sand dunes, and the lowest in sub-climax stage S. vulgaris on fixed dunes. The genetic differentiation among the populations was small (G_st=0.1761), and 82.39% of it was within the populations. Cluster analysis demonstrated that the populations at similar succession stage clustered together, suggesting that the genetic differentiation was closely related to succession stage. The genetic diversity indicated by Nei index ranged in 0.2163～0.2564, and the gene flow (N_m*) was 2.7972, indicating that more gene exchange occurred within the populations, which prevented the genetic differentiation among the populations at different succession stages.