Abstract: Mechanisms of soil microbial variation and relationship with soil physical and chemical factors in desert hinterland greenbelt were investigated through field sampling and laboratory analysis. The results show that soil microbial quantity increases with increase in planting time of forestbelts; and nutrient content and soil fertility status improve remarkably. Among soil microbial flora formation, percentage of bacteria to total microbe is over 80% as dominant species followed by actinomyces, and the least is fungi with less than 0.1% of total microbe. Soil microbial activity is affected by soil environmental factors, especially for soil factors like bulk density, total porosity, moisture content, organic matter and total nitrogen, phosphorus, potassium and available nitrogen, phosphorus and potassium, which have a significant relation with bacteria, actinomyces and fungi. Also soil particle size gradually decreases after forest-belt construction. The findings indicate that planting forest-belt promotes development of sandy soil under saline water irrigation and soil quality improvement, which benefits plant growth. Thus the benefit of windbreak and sandfixation on the Taklimakan Desert highway forestbelt can further be strengthened.