The Tibetan plateau is a unique geographical unit that plays important roles in the formation and evolution of biological species. On the basis of spore morphology, we preliminarily investigated arbuscular mycorrhizal (AM) fungal communities in tropical tussock (TT), warm tussock (WT), temperate desert steppe (TDS), temperate desert (TD), alpine meadow steppe (AMS), alpine steppe (AS), alpine desert (AD), and alpine desert steppe (ADS) environments in southeastern to northwestern Tibet (altitude > 3500 m; mean annual temperature difference > 20 ℃; mean annual amount of precipitation difference > 800 mm), including plateau tropic, subtropic, temperate, subfrigid, and frigid zones. The results showed that the community similarity of AM fungi in different types of grasslands was generally low, and the type of environment had an important effect on the AM fungal community. Community similarity of AM fungi in different types of grassland demonstrated a decreasing trend from southeastern to northwestern Tibet (Jaccard similarity coefficient decreased from 0.52 to 0.20). Changes in the composition and structure of the AM fungal community increased gradually. AM fungal community similarity for the same plant species (including a broad spectrum of species and species endemic to the Qinghai-Tibetan Plateau) in different grasslands was also different. With a gradually aggravated degree of cold and drought in the grasslands along the environmental gradient from southeastern to northwestern Tibet, the abundance of AM fungi species, especially the number of species, showed significantly decreasing trends, according to the Shannon-Weiner index (P < 0.05). At the same time, spore density demonstrated dramatically increasing trends, and the proportion of dominant species in relation to the Shannon-Weiner index also showed a tendency to increase. This indicated that although the diversity of AM fungi showed decreasing trends, their survival and adaptability to the environment tended to improve. The effects of altitude, soil pH, effective phosphorus, and organic carbon content on AM fungal communities were significant, whereas the effects of altitude on the hydrothermal environment determined the changes in the soil environment. Therefore, AM fungal community composition was determined by the comprehensive effects of a dramatic increase in pH and soil organic carbon and a dramatic decrease in effective phosphorus content due to the gradually increasing altitude and degree of cold and drought. Our results have an important reference value for the further understanding of the production and maintenance of organism diversity in the Tibetan Plateau.