The invention discloses a soil culture medium suitable for dry-land 
afforestation and a preparation method thereof. The soil culture medium is prepared by effectively performing compound-mixing on raw materials including clays, 
bentonite, 
organic matter, 
plant fibers, aggregating agents, water-retaining agents, rooting 
powder, controlled-release compound 
fertilizer and clear water. According to the volume ratio of each component to the culture medium, the clays account for 25-30 percent, the 
bentonite accounts for 2-3 percent, the 
organic matter accounts for 30-35 percent, the 
plant fibers account for 10-15 percent, the aggregating agents account for 0.03-0.05 percent, the water-retaining agents account for 0.1-0.3 percent, the rooting 
powder accounts for 0.0005 percent, the controlled-release compound 
fertilizer accounts for 0.8-1 percent, and the clear water accounts for 17-32 percent. The invention also discloses a preparation method of the soil culture medium. The soil culture medium has a good aggregation structure and strong functions of 
water conservation, water retaining, 
fertilizer retaining and ventilation, is rich in 
nutrition and can be absorbed and utilized by nursery stock in a balanced and slow-released manner; the added rooting 
powder can promote the nursery stock to take root early; the planting of the nursery stock is not restricted by seasons; the nursery stock do not need to be watered and conserved after being planted; and the 
survival rate of 
afforestation is high. The preparation method is novel and controllable, and the consumption is low.