A trail was conducted to reveal the distribution of soil bacteria，epiphyte，actinomycetes, nitrobacteria, oxygenic azotobacteria and cellulose-decomposing bacteria at 0—20 cm depth under 4 different habitats in the ecotone in south fringe of Mu Us sandy land. The results showed that: the number of actinomycetes was gentle slope hilly ridge>saline bottomland>fixed and semi-fixed dune>shifting and semi-shifting dune, the order of other groups of microbe number were gentle slope hilly ridge>fixed and semi-fixed dune>saline bottomland>shifting and semi-shifting dune. Bacteria number was the most among all groups of microorganisms and accounted for 70 percent of the total microbe. For the vertical distribution of various groups of microbe, the number of bacteria, actinomycetes, total microbe and oxygenic azotobacteria in shifting and semi-shifting dune were 5—20 cm>0—5 cm, other groups of microorganism under different habitats all were 0—5 cm>5—20 cm.