【Objective】In fragile ecosystems of the arid regions, soil revegetation effect is closely related to soil conservation effect. Haloxylon Ammodendron forest play a quite important role in soil quality evolution in oasis-desert ecozones by protecting and ameliorating the soil. Especially its wind-breaking and sand-fixing effects and its generation of litter, which decomposes and transforms into organic matter and soil nutrients, are the most direct external environmental factors that affect soil quality evolution the most significantly. To explore soil conserving and restoring effects ofHaloxylon Ammodendronforests, affecting factors of the effects and relationships between the factors, and internal mechanism of the effects, stands of Haloxylon Ammodendronforest different in age were selected for the study in an attempt to provide a theoretical basis for management of soil quality in the Hexi Oasis-desert Ecotone.【Methods】The paper adopted the concept of space as a substitute for time in typical sampling in the ecozone. Three stands of Haloxylon Ammodendron forest different in age (20a, 30a and 40a)’ and a tract of bare land were set for long-term monitoring and soil sampling for analysis of soil mechanical composition, chemical properties, microbial population and enzyme activity, and multiple comparisons, variance analysis and correlation analysis were used to analyze variation rules of and relationships between the factors.【Results】Results show that soil protecting effects of the forest varied with growth and age of the forest. Wind decreased gradually in speed when approaching the forest. The effect was more obvious at the lee side than at the windward side. At the height of 20 cm, 50 cm, 100 cm and 200 cm above the ground in the forest wind speed decreased by 13.75%, 14.55%, 15.0% and 7.34% or more, respectively. Obviously the wind reducing effect is higher in the middle and lower part of the forests than in the upper part, and about 1.05~2.04 times of that at the top of the plants. With the forest growing in age, the magnitude of wind reduction increased from 12.66% to 20.41%. In terms of wind reduction magnitude at the height of 20cm, 50cm and 100cm above the ground, the three stands displayed an order of stand 30 years old > stand 40 years old > stand 20 years old, but in terms of at the height of 200 cm, they exhibited a different order, i.e. stand 40 years old > stand 30 years old > stand 20 years old. In the stands of Haloxylon Ammodendron forest, regardless of age, the proportions of silt and clay were much lower that those of coarse sand and fine sand in the surface layer, and with the increase in soil depth, the contents of silt and clay decreased slightly, but were still significantly higher than that in the bare land. With the forest growing in age, the content of silt and clay increased and the content of coarse sand decreased, and both leveled off at the age of 30. The stands all peaked in nutrient content, microorganism population and enzyme activity at the age of 30, exhibiting an order of stand 30 years old > stand 40 years old > stand 20 years old, and were all over 1.02 times higher than those in the bare land. The content of soil nutrients decreased with soil depth,. The populations of soil actinomycetes and fungi and the activity of invertase was the highest in the surface soil, then in the subsoil layer and the lowest in the bottom layer. The activity of catalase and alkaline phosphatase was just in a reverse order. No obvious regularity was observed for soil bacteria in population, but good relationships were observed of the factors of the soil conservation effect of Haloxylon Ammodendronforest with soil mechanical composition, soil nutrient status, and microorganism population and enzyme activity. Wind breaking effect of the forest was significantly related to soil mechanical composition (r＞0.87).【Conclusions】Considering the soil protecting and ameliorating effects of Haloxylon Ammodendronforest, the forest 30 years in stand age is the most suitable for the local habitat conditions and the highest in soil conserving effect. So in management of Haloxylon Ammodendron forests over 30 years in stand age, it is recommended to cut down trees selectively for thinning, and adopt water conserving and nutrient supplementing measures and some others so as to ensure healthy growth of the forests and enable them to keep on playing their ecological role in wind breaking and sand fixing in the ecozone.