Abstract: This paper concerns the analyses of niche breadths of and overlaps between several plant species in 3 Kobresia communities in the Haibei Research Station using the formula described by Levins and Pianka. Our results show that the dominant species in the three Kobresia communities have greater niche breaths than their companion species. Kobresia pygmaea have niche breadths of 0.918, 0.896 and 0.910 on the gradients of soil water potential, incident light intensity and slope aspect, respectively. K. humilis and K. tibetica have niche breadths of 0.875 and 0.866, respectively, on the soil water potential gradient. The niche Overlaps are higher between the species that have greater niche breadths than between those that have relatively narrower niche breadths. The niche overlaps show a decreasing trend among congeneric species that have similar biological and ecological characteristics. The niche overlaps between K pygmaea and K. humilis are 0.671, 0.719 and 0.686 on the gradients of soil water potential, incident light intensity and slope aspect, respectively. Our results also show that the niche overlaps between some weeds and high-quality grasses are rather high. This might have been attributable to the suppression of high-quality grasses due to long-term overgrazing and habitat degradation.