Soil fauna play an important role in terrestrial ecosystems, directly or indirectly modulating the availability of resources for other species by changing biotic or abiotic materials. Knowledge of temporal variability of soil fauna is crucial to understanding soil community dynamics and food webs, especially in variable systems such as an alpine meadow ecosystem. A typical alpine meadow in Zoigê County grassland located on the eastern edge of Qinghai-Tibet Plateau, China, was studied to document the composition, diversity, and seasonal variations of soil meso- and microfauna communities in alpine grasslands. Six 50 m × 50 m plots were established using permanent markers. Five observations were conducted from July 2008 to October 2009 and six samples in size of 50 cm × 50 cm were investigated in each plot every time. Tullgren and Baermann's methods were used to extract 9318 soil meso- and microfauna individuals and these were classified into three phyla, seven classes, and 88 taxonomic groups. The mean density of the soi1 meso- and microfauna community was 39941.67 ind./m². Nematoda dominated, accounting for 91.50% of the individuals in the soil meso- and microfauna community; Arachnida (mainly Acarina), Collembola, Oligochaeta (mainly Enchytraeidae) and Insecta (mainly Diptera larvae and Coleoptera larvae) made up 3.73%, 2.55%, 1.12%, and 1.07%, respectively. The community individual density, taxonomic group, and diversity indexes of soil meso- and microfauna varied by season both intra- and inter-years, with minimum numbers of both individuals and taxonomic groups recorded in July and the maximum in October. Significant seasonal changes were recorded in community taxonomic groups, individual density, density-group indices, the Shannon and Pielou indices (P<0.01), and the significant change was also found with Simpson Index (P<0.05). The seasonal density change trends within the five major classes, Nematoda, Arachnida, Collembola, Oligochaeta and Insecta, were similar to each other, and had significant differences (P<0.05). The values of the Sorensen Index among the seasons were lower than the Morisita-Horn Index, implying the seasonal change has a relatively stronger influence on the taxonomic composition of the meso- and microfauna community than on the abundance of the dominant taxonomic groups. Pearson correlation analysis shows the taxonomic group (P<0.01) and individual density (P<0.05) of the community have a significantly inverse relationship to air and soil temperatures (depth 0-15 cm) but are not significantly related to monthly precipitation; the same results were found with the individual densities of Collembola, Oligochaeta and Insecta, but not to those of Nematoda and Arachnida. All results suggest the taxonomic composition and diversity of soil meso- and microfauna communities in an alpine meadow ecosystem on the eastern edge of Qinghai-Tibet Plateau have obvious seasonal characteristics; seasonal changes in temperature are the main factor influencing those changes. In addition, the effects of temperature and precipitation on the soil meso- and microfauna community also implies increased global temperatures will have adverse short-term effects on soil fauna in the alpine meadow ecosystem.