Abstract: The sample plot investigating method was used to research insect communities in three different growth phrase of tropical rain forest (gap phase,building phase,mature phase) of Xishuangbanna in September,1997 and April,1998.The species and individual composition of insect communities were studied,the DMA,J,d,Ds,H index were used for comparing the diversity of insect communities in three habitats.The results showed that the total number of insects collected were 2 455 belonging to 15 orders with Diptera,Hymenoptera and Coleoptera as the dominant groups and Lepidoptera as the normal groups.There were the most number of species and individuals of insect communities in building phase (secondary forest).The richness and dominance of insect communities were the largest in building phase,but the evenness of gap phase was the largest.The Shannon-Wiener diversity index in mature phase was the largest,and it got higher with the increase of growth stage.The species composition similarity between mature phase and building phase of tropical rain forests was the highest,but it was lower between building phase and gap phrase.