Evaluation of precipitation and nitrogen (N) deposition in desert ecosystems helps to elucidate the reaction of desert ecosystems to future environmental changes. An in-situ field experiment was established to examine the influence of a long-term enhanced precipitation and N deposition on the photosynthetic traits and physiological characteristics of Haloxylon ammodendron in the Gurbantunggut Desert, northwest China, throughout the growing season in 2014–2016. Results showed a significant interaction between precipitation and N applications. Increased precipitation and N deposition and their coupling could significantly improve photosynthetic capacity, alter the variability in amplitude of water potential and change the content of substances regulating osmotic pressure in H. ammodendron . According to the comprehensive evaluation of H. ammodendron’s adaptability using six different water and N coupling models, a combination of a 30% increase in precipitation and a 30 kg N ha −1 yr −1 addition in nitrogen deposition, or the addition of N at a concentration of 60 kg N ha −1 yr −1 with natural precipitation were beneficial to H. ammodendron growth and development. Hence, changes in the future global environment can be anticipated to be beneficial to H. ammodendron growth.