To understand the species, species distribution, the dominant species and their interspecies interaction of chigger mites on Eothenomys miletus(a dominant species of rats) in Yunnan.The rats were captured with mouse traps in 16 counties (or cities) during 2000-2004. All mites on the surface of two auricles of the hosts were collected and identified. The patch index (m*/m) and the coefficient of association (V) were adopted to judge the spatial distribution patterns and interspecies interaction of the dominant chigger mite species among different individuals of the rats (E. miletus).1157 individuals of E. miletus were captured from 16 counties (citys). 37613 chigger mites (belonging to 3 subfamily, 9 genus and 80 species) were collected from the auricles (body surface) of 1157 rat hosts with a high "overall mite infestation rate" (68.2%) and "overall mite index" (32.5). Six species of mites were found dominant on E. miletus: Leptotrombidium scutellare, Leptotrombidium sinicum, Helenicula simena, Leptotrombidium eothenomydis, Herpetacarus hastoclavus and Leptotrombidium hiemalis. The distribution of the chigger mites among different individuals of E.miletus showed an aggregation pattern. Both positive and negative association existed between each two dominant species of chigger mites.The species composition of chigger mites on Eothenomys miletus is complex with abundant individuals, which reflects a high species diversity of the mites. The main species of chigger mites tend to an aggregation on the body surface of E. miletus.