[Objective] To study the hydrochemical characteristics of the surface water and groundwater as well as their effects on the Populus euphratica growth in desertification area, in order to provide theoretical support and scientific basis for the conservation and rejuvenation of P. euphratica.[Methods] Field investigation was conducted and the samples were collected at Xinjiang Tarim P. euphratica national nature reserve. The hydrochemical characteristics of middle reaches of Tarim River and their effects on growth of P. euphratica were studied.[Results] ① In the studied area, hydrochemical types of the surface water were mainly SCa_Ⅲ or ClNa_Ⅲ (Based on the O. A. Arliekin's classification). The pH value of the surface water was below 8.0. The pH value of the surface water was 7.42~7.82 where P. euphratica grew well. ② Total hardness and total alkalinity, TDS of overflowing river were ranged as 325.3~769.5, 142.6~290.3 and 782.2~1 037.5 mg/L, respectively. P. euphratica was able to grow normally in the environment of brackish water (TDS>1000mg/L). The water in this nature reserve was contaminated by the drainage of farmland, and the ammonia nitrogen content was 0~0.45 mg/L.[Conclusion] The distribution of the P. euphratica with different diameters characterized an inverted pyramid structure, thus its rejuvenation was confronted with difficulty.