The community characteristics of soil nematodes in a Stipa baicalensis steppe in Inner Mongolia under different nitrogen treatments (0, 15, 30, 50, 100, 150, 200, 300 kg N hm^-2 a^-1) were studied by field investigation and sample analysis using the morphological classification method. In total, 52 genera were identified in all the samples. The dominant species were Helicotylenchus, Acrobeles, and Aphelenchus. Soil nematodes showed an obvious surface convergence phenomenon, and their relative density was not significant. Based on the functional groups, the addition of Bacterivores nematodes and Predators/Omnivores showed a negative correlation with the increase in nitrogen application level. The ecological indices such as abundance (SR), diversity (H'), and evenness (J') of soil nematodes increased with the increase in nitrogen application level, reaching their maximum values at N50. In all treatments, the pathway index was less than 0.75, indicating that fungi decomposed organic matter in the soil. The ecological indicators showed that nitrogen application at N100, the soil pH value decreased significantly, the nitrate nitrogen and ammonium nitrogen contents increased significantly, the soil life history k countermeasures were significantly reduced, and r countermeasures were significantly increased,significantly altering the soil nematode community structure.