Abstract:Based on field survey, the effects of artificial Ulmus pumila forest on the species diversity of temperate grassland in Siziwang Banner of Inner Mongolia were studied. The results showed that U. pumila forest had obvious effects on the species diversity of grassland. With increasing density of U. p umila, the Patrick’s richness, Pielou’s evenness and Shannon-Wiener index o f grass species under the forest had a decreasing trend, and were higher nearby the forest than far from the forest. The habitat inside the forest was favorable to Silene jenisseensis, while that nearby the forest was favorable to Heteropappus altaicus, Pocockia ruthenia, Potentilla bifurca, Leymus secalinus and Cleistogenes squarrosa, suggesting that to blindly exclude forestatio n on grassland could be less scientific, while properly afforesting U. pumila on the sides with relatively abundant soil moisture should be available to th e conservation of plant diversity in temperate grassland regions.