By setting up the controlled-experiment with soil water content,we analyzed the root growth and architecture of Populus euphratica seedling to indicate the relationship between the root development and soil water content.The results showed that:(1)drought stress caused the increase of root to shoot ratio to adapt to the arid environment.(2)A certain degree of drought treatment promoted the development of root morphological characteristics and biomass.But excessive drought stress or soil water content may inhibit root growth.Root was most developed under the 15% water content with continuous water treatments.(3)Ration of width to depth of seedling’s root system was less than 1 with both water treatment,the root have a high ability to grow deeper.The ration under intermittent water treatment was significantly less than those under continuous water treatment.There is a significant positive correlation with water content for both water treatments.(4)Topological index of both water treatment was close to 1 and the root branching patterns were herringbone-like,root branching ability was week.The root extension strategy was helpful for the seedling to survive in dry and infertile soil environment.The index was significantly negatively correlated with the water content for both water treatments.(5)A total of 10 parameters of root architecture were analyzed by the principal component analysis.The parameters of total root length,total root surface area,ration of width to depth and topological index could well present the root architecture characteristics of P.euphratica seedling’s root with both water treatments.We concluded that P.euphratica seedling adapt to the arid environment through the establishment of herringbone-like branching patterns,increase of the vertical longitudinal extension ability and root to shoot ratio.Soil water factor played an important role in regulating P.euphratica seedling’s root growth and architecture.The ability to response to soil water content of P.euphratica seedling’s root system may lead to the success to adapt to heterogeneity in soil water.