Soil nematodes are key components of the soil food web and are highly sensitive to environmental changes. To investigate the effects of long-term nutrient addition on soil nematode community structure in meadow steppes, this study was conducted based on a long-term field experiment platform for nutrient addition established in 2010 in the Stipa baicalensis meadow steppe of Hulunbuir City, Inner Mongolia. Four treatments were set up: N addition (100 kg N·hm-2·a-1), P addition (100 kg P·hm-2·a-1), combined N and P addition (100 kg N·hm-2·a-1+100 kg P·hm-2·a-1), and a no-fertilization control (CK). The relationship between nematode community structure composition and ecological index changes and environmental factors was explored. The results showed that compared with CK, long-term nitrogen and phosphorus addition significantly reduced the abundance of soil nematodes, with the order of N (28%) < P (47%) < NP (51%), and the community composition was significantly different, and the species tended to be single. Long-term nitrogen and phosphorus addition increased the proportion of c-p1 group nematodes, decreased the proportion of c-p4 and c-p5 groups, and the overall nematode life history was biased towards r-strategist. The NCR index was increased, indicating that the degradation of soil organic matter was mainly regulated by bacteria. Floristic analysis showed that the soil food web was in an unstable degradation state after long-term nitrogen and phosphorus addition. The soil pH decreased after long-term nitrogen and phosphorus addition, which directly inhibited the abundance of fungivores. The availability of AP was changed by phosphorus fixation, which limited the microphagous nematodes (Ba, Fu) and total nematode abundance (TNN). At the same time, it promoted the accumulation of aboveground biomass (AGB), but the aboveground carbon input under the background of acidification failed to effectively support nematode resources, but aggravated environmental instability. Under the synergistic effect of the three, the number of nematodes decreased, the diversity decreased, the community structure simplified and the food web was unstable. The above results provide a scientific basis for soil nutrient management in meadow steppe.