Abstract: The effects of human activity on community structure of small mammals in a wet evergreen broadleave forest of Ailao mountain has been described.The results show that:(1)Three habitats or biotopes can be divided in this area,namely,the primary forest,the secondary forest which had been primary forest and destructed by human activity as well as the grassland which had been primary forest and destructed severely by human activity.(2)There are 16 species in the primary forest and the capture rate is 9.81%,of which,Apodemus draco and Neotetracus sinensis are the dominant species.Six species in the secondary forest and the capture rate is 1.18% and A.draco and Rattus niviventer are the dominant species.Five species in the grassland and the rate is 0.92% and the dominant species is Micromys minutus.(3)Average density and biomass is 36.05 ha and 917.18 g/ha in the primary forest,5.30 ha and 205.03 g/ha in the secondary forest as well as 4.35 ha and 107.15 g/ha in the grassland.Therefore,the conclusion should be:The community composition,number and relative abundance of small mammal species have been changed.The increase of disturbed intensity of forest leads to the declines of the species diversity,moreover,the larger of the disturbance intensity,the smaller of the density and biomass.