Abstract: To explore the responses of grassland community characteristics and species diversity to the altitudinal gradient and human activities, the species composition and plant life form of grassland community along altitudinal gradients from 3 485 to 3 650 m in the west-wing area of Gahai Lake, Gansu province, located in the eastern region of Qihai-Tibet Plateau, were investigated. The data showed that 59 species were found in this region, which belongs to 20 families and 46 genera. Most distribution type of these genera is the temperate, and the majority of these species are the perennial and non-leguminous nitrogen-fixing plants. The six grassland community types were classified along the altitudinal gradients, namely Poa annua-Anemone obtusiloba community, Potentilla plumose-Plantago depressa community, Stipa purpurea community, Poa annua-Koeleria cristata community, Poa annua-Kobresia myosuroides community, and Kobresia myosuroides-Cyperus community. The dominant species in the natural grassland are mostly consist of Gramineae and Cyperaceae families, while the species were replaced by the Potentilla plumose-Plantago depressa and Stipa purpurea in the human strongly active area, and herein human activities strongly influence the grassland community characteristics. In addition, the negative relationships between altitude and indexes of species diversity (such as, species abundance, species density, similarity index, and the number of common species) were also found. Obviously, both altitude and human activities strongly affect the community characteristics and diversity of the alpine grassland, even the human activities are more pronounced. Therefore, in order to sustain the species diversity and ensure sustainable development of alpine grassland, we should take the reasonable and effective protection and minimize the impact of human activities.