Abstract: Tamarix ramosissima is a dominant species in the lower reaches of the Tarim River, and plant survival and growth is affected by a double stress of nutrient and seasonal water deficit in the sandy soils in this locality. More detailed information on the stress responses of this species will assist the process of ecological restoration in the Tarim River lower reaches. Four soil watering regimes (D₁-20%, D₂-35%, D₃-50% and D₄-75% of relative field capacity) and two forms of fertilizer N; KNO₃ (N₁) and NH₄Cl (N₂) were provided in order to explore drought stress and nitrogen responses. Changes in plant growth and photosynthetic physiological traits were measured shortly before flowering. Key results were: 1) Water is the main limiting factor for growth of T. ramosissima seedlings, and an increase in plant height occurred with the enhancement of N supply. For D₁, ammonium nitrogen significantly affected plant height, but nitrate nitrogen was more significant for D₄. 2) When seedlings were subjected to water stress, the two forms of nitrogen affected chlorophyll content differently. At higher soil moisture content in D₂ and D₃, chlorophyll b was increased more by ammonium nitrogen supply than chlorophyll a. At D₃, the nitrate nitrogen was only increased the contents of chlorophyll a. 3) With enhanced N supply, we found an increase in photosynthetic efficiency (φ_PS(Ⅱ)-quantum yield of PSⅡ and ETR-estimated electron transport rate). At D₁ and D₃ the effect of ammonium nitrogen was more significant, but at D₂ the effect of nitrate was more significant. 4) Ammonium nitrogen was more easily absorbed by the root to promote total biomass accumulation, and nitrate nitrogen significantly increased the total biomass of seedlings only in the D₄ soil water regime. With enhancement of N supply, the specific root length decreased significantly when the soil water content is D₂ and D₃, it indicated that aboveground biomass of plant occupied more assignments. Under reduced water supply, the root:shoot ratio of nitrate nitrogen was significantly increased, and captured nitrogen appears to have been consumed by growing roots. With adequate water (D₃), ammonium nitrogen effects root:shoot ratio was significantly decreased, and the N appears to have been used to increase crown diameter. Therefore, water is the key factor in management of T. ramosissima seedlings, and when seedlings absorb nitrogen, the combined effect of water and nitrogen can improve seedling photosynthesis and growth and allow the seedlings to grow successfully in these undesirable surroundings.