Abstract: 【Objective】 An important afforestation tree in arid region. 【Methods】 To explore the effects of nitrogen fertilizer on drought resistance of Calligonum caput-medusae Schrenk seedlings, Two groups of water treatments (deficit water supply and normal water supply) and two groups of nitrogen treatments (no nitrogen application and nitrogen application) were set up in pot experiment to determine the physiological and biochemical indexes of assimilated branches of seedlings. 【Results】 (1) Compared with normal water supply, the relative water content (RWC), midday water potential (Ψ_m), maximum stomatal conductance (g_s), chlorophyll content (Chl), apparent quantum efficiency (Φ) and soluble sugar (SS) contents of assimilated branches were significantly decreased under deficit water supply. The content of proline (Pro) increased significantly. (2) Compared with no N application group, N application slowed down the relative water content of the assimilated branches of A. capulosa seedlings under deficit and normal water supply, but it was not significant; Compared with normal water supply, nitrogen application under deficit water supply reduced the assimilative branch water potential of A. capillata seedlings. (3) Under normal water supply, the contents of Pro and SS were increased by nitrogen application, while the contents of malondialdehyde (MDA) were significantly decreased (P<0.05). Under deficient water supply, nitrogen application increased the content of superoxide dismutase (SOD), Pro and SS (P<0.05), but significantly decreased the content of MDA (P<0.05). 【Conclusion】 The physiological activity of Jujube japonica seedlings is affected by the availability of soil water, and nitrogen application can reduce the effect of drought stress on them. Nitrogen application increases the activity of antioxidant enzymes and the concentration of cytosoles in the deficient and normal water supply, and helps the seedlings to overcome oxidative stress, reduce damage and increase osmoregulatory substances.