[Objective] The effects of soil conditions on species distribution and diversity under Haloxylon ammodendron Forest were researched to provide references for biodiversity preservation.[Methods] Methods of canonical correspondence analysis and generalized additive model were used to analyze the effects of soil factors on species distribution and diversity under Haloxylon ammodendron forest in Mosuowan. The forest is located in the southwest of Gurbantunggut Desert, have three types as natural, natural-artificial and artificial Haloxylon ammodendron forests.[Results] (1) Soil water(SW), electrical conductivity(EC) and biological crust were the main factors of species distribution. Salsola ruthenica and Lappula semiglabra tend to distribute in high levels of soil water and electrical conductivity; whereas Timonium leptolobum prefer growing in soil with high pH value, for Corispermum hyssopifolium, conditions of low soil water and electrical conductivity, and of having biological crust, were seemed to be more preferable. Neotorularia korolkowii and Atriplex patens have good adaptability and can establish and distribute in all three forests. Natural regeneration of Haloxylon ammodendron was found increased with the decreases of SW and EC, increased with the increase of biological crust. (2) SW, EC, pH value and soil structure were the main influence factors of diversity. There were high significant positive correlations(p<0.01) between species diversity indices and contents of SW and silt, and there were significant negative correlation(p<0.01) between species and values of EC and pH. Under the condition of low soil water, about 2.19% and 6.28%, soil water was found to be the most factor that influence species diversity. When SW>8%, species diversity tend to be stable when SW increase. Species diversity decline obviously when pH value>9.0.[Conclusion] Undergrowth species distribution and diversity in Haloxylon ammodendron forest were influenced by a variety of soil factors, in which SW and EC played the most important role.