[Objective] Haloxylon ammodendron is the main species of shrubs planted to establish a sand-fixing vegetation in the arid region of Northwest China. Evolution of the sand-fixing vegetation system after Haloxylon ammodendron is planted, is influenced by soil development. [Method] To explore how the soil develops under the Haloxylon ammodendron forest in that region, plots of Haloxylon ammodendron forests along an age sequence, i.e. of 0-, 3-, 6-, 9-, 16- and 40-year-old, in the edge of the Pingchuan Oasis in Linze County in the middle of the Hexi Corridor were selected in the study and soil samples were collected from the plots for analysis of soil properties. And then discussion was made of plant-soil interactions and their influences on evolution of the vegetation ecosystem. [Result]Results show that soil clay and silt, soil organic carbon (SOC) and soil total nitrogen (TN) all increased in content or concentration gradually with the vegetation living on, but the phenomenon became obvious only in the 0~20 cm surface soil, 9 years after the vegetation was established. However, salt accumulation occurred throughout the whole soil profile (0~100 cm in depth), especially significant in the 20~80 cm soil layer. SO₄^2-,Ca²⁺ and Na⁺, the main components of soil salt, increased with the age of the plantations and accumulated significantly in the soil profiles of the 16- and 40-year-old plots. In comparison with non-vegetated land of shifting sand, the Haloxylon ammodendron planted plot, 16 and 40 years old, was 3.3 time and 5.7 times, respectively, higher in SOC concentration in the 0~10 cm surface soil layer, and 5.4 and 6.5 times higher in mean salt content in the 0~100 cm soil profile. [Conclusion] All the findings in this study suggest that soil salt accumulates faster than SOC and soil nutrients in the soils under Haloxylon ammodendron in its growing and developing process. Such a salt accumulation rate may affect setting-up and development of herbaceous plants, and in turn influence stability of the artificial vegetation system. Along the 40-year-long age sequence, the soil under Haloxylon ammodendron plantation developed from Aridic Psamments to Aridic Orthents and will eventually turn into Calciorthids as affected by the continuous salt accumulation and calcafication process. Hence further observations and studies are needed to verify development of the soil.