To reveal the impacts of exotic plant invasions on soil ecosystem, we studied the effects of leaf litter decomposition of the invasive plant Ambrosia trifida on soil nematode community structure and diversity. Leaf litters of the invader and the co-occurring native Artemisia selengensis collected in Shenyang were added on soils in micro-ecotrons, and decomposed for different periods. Then we collected the soils and analyzed nematodes. The results showed that the invader had a higher litter decomposition rate than the native species, which may be associated with the higher nitrogen concentration for the invader. With increasing treatment time the differences in the densities of bacterivores, fungivores, and total nematodes increased between treatments. After 45 days of leaf litter decomposition, the densities of total nematodes and fungivores were significantly higher in invasive plant litter treatment than in native plant litter treatment. After 90 days of treatments, the densities of bacterivores and fungivores were significantly higher in invasive litter treatment than in native plant litter treatment. There was an increasing trend in enrichment index but a declined trend in structure index with increasing treatment time. After 90 days of treatments, the structure index was significantly higher in the invasive plant litter treatment than in the native plant litter treatment, while the difference in soil nematode diversity index was not significant between treatments. Our results suggest that leaf litter decomposition of the invasive species facilitates soil nematode proliferation and alters its community structure, but has no effect on α diversity.