【Abstract】 Objective To investigate the community structure of fleas on small mammals in eight counties of southern mountainous areas in Yunnan. Methods Small mammal hosts were captured from eight counties selected randomly in southern mountainous areas and fleas were collected from the body surface of each host. Richness (S), Shannon?Wiener’s diversity index (H′), evenness (J′) and dominance index (C′) were used to measure the community structure of fleas on the hosts. Results There were 3184 small mammals captured, which belonged to 21 species,13 genera, 5 families and 4 orders. A total of 1767 fleas were collected from the small mammal hosts and were classified into 15 species, 13 genera and 5 families. There were seven dominant small mammals like Rattus tanezumi, Mus caroli, M.pahari, R.norvegicus, Suncus murinus, R.rattus sladeni and Niniventer fulvescens, and the dominant fleas were Xenopsylla cheopis, Nosopsyllus (Nosopsyllus) wualis and Leptopsylla segnis. Conclusion There are few fleas in the southern mountainous areas of Yunnan which biodiversity is lower than that in others.