ObjectiveTo analyze the community structure and dynamics of parasitic fleas on the body surface of host animals and nested fleas in different seasons in the natural foci of wild rat plague in Yulong County，Yunnan Province， to explore the relationship between seasonal fluctuation of fleas and the prevalence of plague among animals， so as to provide evidence for plague prevention and control in the natural foci. MethodsNanxi Village， Huangshan Town， the core area of plague epidemic in Yulong County， was selected as the monitoring sample area in December 2019 （winter）， August 2020（summer）， October 2020（autumn） and March 2021（spring）. Host animals were captured by rattrap at night and rat nests were excavated for collecting parasitic fleas on host animals and rat nest fleas in different seasons. Excel 2010 and SPSS 26.0 software were used to analyze the data， and Chi square test was used to compare the rate. Community ecological indicators were used to analyze the community structure and species diversity of the host animals and their parasitic fleas. ResultsA total of 355 vector fleas were captured， belonging to 7 species of 5 genera in 2 families. 441 small animals were captured and 138 rat body fleas were detected with the flea infection rate of 14.51% and the flea index 0.31. 96 effective rat holes were excavated and 217 fleas were detected with the flea infection rate of 35.42% and the flea index 2.26. Among the four seasons， the flea infection rates of rat body and rat nests were higher in summer and winter， showing a significant difference in general （χ²=15.851， P<0.01； χ²=16.398， P<0.01）. The dominant species of flea community were Ctenophthalmus quadratus， Stenischia humilis， Neopsylla specialis and Frontopsylla spadix， with a dominance index of 0.434， 0.254， 0.180 and 0.110， respectively. The diversity and evenness of rat body fleas showed a distribution characteristic of decreasing， increasing and then decreasing again with season changes， and both were the highest in spring， while the ecological dominance showed an opposite trend. The diversity and evenness of rat nest fleas showed a distribution characteristic of increasing first and then decreasing in summer， autumn and winter， with the highest in autumn， while the ecological dominance was diametrically opposite. ConclusionThe fleas community structure is relatively stable in Yulong County， but the number of species in the community is unevenly distributed by seasons， and the status of dominant species is prominent. Local authorities should carry out timely preventive deratization and depulization measures according to the results of daily monitoring， so as to effectively avoid the prevalence and spread of plague among animals in plague foci.