The species-abundance distribution of the gamasid mite community on 25 species of small mammals in western Yunnan, China was mathematically described. On the basis of the species-abundance distribution, the expected total numbers of species were further estimated according to a mathematical process. In a semilogarithmic rectangular coordinate system with a logarithmic scale in X-axis and a common arithmetic scale in Yaxis, the species-abundance distribution of the gamasid mite community can be fitted by a lognormal distribution theoretically with 0.8263 of the coefficient of determination (R²). In the studied community, the dominant species with abundant individuals and the rare species with only one individual were much less prevalent than the common species with a moderate number of individuals. The expected total number of species of the gamasid mite community were estimated to be 79, which was 21 more than the actual 58 collected species and this suggests that there were about 21 species that were missed in the actual field investigation.