The aim of this study is to disentangle the effects of planting artificial oat grassland in the natural alpine grassland on soil nematode communities on Qinghai-Tibetan Plateau. Investigations were respectively performed on the soil nematode communities in an oat grassland (OG) cultivated for two years and a natural grassland (NG) in Hongyuan County, northwest Sichuan, in July and September 2014. Soil nematodes were extracted from soil samples using Baermann method in the laboratory. A total of 10179 soil nematodes were extracted and affiliated with 2 classes, 8 orders, 50 families, and 143 genera. The community abundance was 477 individuals 100 g^-1 dry soil. The taxonomic composition of the soil nematode communities in OG differed from those in NG driven by the determining genera of Acrobeloides, Protorhabditis, Filenchus and Rotylenchus. The abundance of nematode communities, functional groups of bacterivores and fungivores, the maturity index (MI) were significantly higher in OG than those in NG (P<0.01; P<0.05; P<0.001; P<0.01), whereas an opposite pattern was observed for the plant parasitic index (PPI) (P<0.05). Taxonomic richness and Shannon-Weiner index were both strongly enriched in September for OG and NG, compared to those in July (P<0.05). However, a higher Simpson index and larger abundance of bacterivores and fungivores were observed in July (P<0.05; P<0.001; P<0.01) for OG. The results of canonical correspondence (CCA) analysis and multiple regression analysis showed that soil characteristics (pH, soil organic matter, total N, available soil P and soil water content) exerted an overriding influence on the soil nematode communities. Overall, the study indicated that the transformation from natural alpine grassland into artificial oat grassland led to an enrichment in the overall soil nematode community abundance and a clear variation in the community structure. Specifically, the relative abundances of the bacterivores and fungivores increased, and the trophic structure was dominated by bacterivores rather than plant-parasites. In addition, the temporal stability of soil nematode communities decreased along the transformation.