Warming can decrease feeding activity of soil organisms and affect biogeochemical cycles in alpine ecosystems. Ants (Formica manchu) are active on their nest surface, and prefer a hot and dry environment. Therefore, warming may provide a favorable environment for their activity. We hypothesized that ants might benefit from warming and increase the robustness of ecosystem functions to warming. To test this hypothesis, we examined the effects of ant nests (ant nest absence vs. ant nest presence) and warming (ambient temperature, + 1.3°C and + 2.3°C) on litter decomposition, soil properties and the plant community in an alpine grassland ecosystem. Decomposition stations with two mesh sizes were used to differentiate effects of microorganisms (0.05mm) and macroinvertebrate (1cm) to litter decomposition. Ant nests increased litter decomposition with and without macroinvertebrates accessing the decomposition station when compared to plots without ant nests. Only the litter decomposition in ant nests with macroinvertebrates accessing the decomposition station was not negatively affected by warming. Plots with ant nests had greater soil organic carbon, nutrient contents and plant growth than plots without ant nests, regardless of warming. Consequently, ant nests can mitigate the negative effects of warming on litter decomposition and improve ecosystem functions under warming.