To explore the soil nitrogen content and composition characteristics of sagebrush desert grassland, a paired experimental design was used to study the effect of grazing exclusion on total nitrogen, alkaline hydrolyzable nitrogen, nitrate-nitrogen, and ammonium nitrogen in different regions of the northern slope of Tianshan sagebrush desert grassland. The results showed that: (1) After grazing exclusion, the soil nitrogen density (0.59~0.79 kg/m²), soil total nitrogen (0.81~1.50 g/kg), soil alkaline hydrolyzable nitrogen (19.44~67.49 mg/kg) did not significantly changed (p＞0.05). (2) The effects of grazing exclusion on soil nitrate-nitrogen (6.41~21.26 mg/kg) and ammonium nitrogen (0.26~2.53 mg/kg) in sagebrush desert grassland were different due to regional differences. After grazing exclusion, the content of nitrate-nitrogen in the soil layer of 0—50 cm in Gongliu and Hutubi plots decreased significantly by 24.61% and 47.25% (p＜0.01) respectively, while Qitai plots increased significantly by 20.95% (p＜0.05). After grazing exclusion, the content of ammonium nitrogen in the 0—50 cm soil layer of the Manas plot increased significantly by 27.98% (p＜0.05), while that of the Gongliu, Bole, and Hutubi plots did not decrease significantly. (3) The contents of nitrate nitrogen and ammonium nitrogen in the soil of sagebrush desert grassland accounted for 0.27%~3.01% and 0.02%~0.42% of the total nitrogen, and with the increase of total soil nitrogen, the proportion of organic nitrogen increased, while the proportion of inorganic nitrogen, nitrate nitrogen, and ammonium nitrogen decreased. (4) Correlation analysis showed that soil total nitrogen, alkali-hydrolyzable nitrogen, nitrate-nitrogen, and ammonium nitrogen were positively correlated with organic carbon and total phosphorus, and negatively correlated with soil bulk density, pH, and electrical conductivity, and ammonium nitrogen was correlated with soil water content. It was positively correlated and negatively correlated with available phosphorus. Partial redundancy analysis showed that the main factors influencing soil physicochemical factors on soil nitrogen were soil organic carbon and soil water content, and the explanation rates were 32.60% and 17.90% respectively. The research results provide scientific data support for revealing the soil restoration and nutrient management of sagebrush desert grassland in the process of grazing exclusion.