The knowledge of food habit and feeding each of herbivores plays very important role in the grassland management for traditional grazing systems. To understand the diet composition and trophic niches of the main herbivores of the Gannan meadow, we measured the dietary composition and food-niche overlaps of four herbivores, Yak, Tibetan Sheep, Himalayan Marmot and Plateau Zokor. First, we conducted a vegetation survey during the fall of 2014 in Luqu, Gannan meadow and collected all the plant species (78 species) to make micro-specimen as the reference for identifying the plant species in the content of stomachs and dejection of target herbivores species. Then we made a vegetation survey by collecting all the plant species in the plot 1 m × 1 m in size to evaluation the food availability. Total of 20 plots were selected randomly from three vegetation plot of 200﹣300 m in length and 100 m in width. The contents of stomach or rejection were collected and washed in distilled water with 2% alcohol. The materials remanents were filtrated by sieve (1﹣0.3 mm) and washed with 5% potassium hydroxide to remove the black color from the plant fragment remains. Samples were passed through ethanol and finally dehydrated with xylene. A permanent slide of each sample fragment was prepared for observation under a microscope. The relative frequency percentage of each plants species in the samples was calculated, and the dietary composition and trophic niches of these herbivores were analysed based on these data. We used Duncans new multiple range method to investigate significant differences in plants species composition between the four herbivores. Sheep and Yaks mainly fed on Hairgrass (Deschampsia caespitosa) and Blysmus (Brylkinia compressus), while Himalayan Marmot took more Tibetan. Cinquefoil (Potentilla anserina) and Krylov Needlegrass (Stipa captillata). Plateau Zokor prefered the shafts and bulb root plants of Saussurea (Sausserua superba), Cinquefoil, Dandelion (Taraxacum mongolicum), Shawls Grass (Elymus nutans). The food niche breadth of Yak, Tibetan Sheep, Himalayan Marmot and Plateau Zokor was 3.38, 3.30, 2.65 and 2.60 respectively. Food-niche overlap was highest in Tibetan Sheep and Yaks which reached at 0.94, followed by Plateau Zokor and Himalayan Marmot (0.76), the lowest value (0.41) was found in Tibetan Sheep and Plateau Zokor, while the whole food-niche overlap of the four mammals was 0.09. The diet composition and food-niche overlaps of four main herbivores provided the overall understanding of those species and their habitat, and may contribute to improving grassland management at local and regional levels.