Abstract: Composition of groups, distribution of individuals and diversity of soil arthropod communities in the tropical montane rainforest and tropical monsoon rainforest of Xishuangbanna were studied in September and December 1999. The results show that the total number of arthropods collected are 6 606 which consist of 23 orders. Acari, Collembola, Hymenoptera and Coleoptera were dominant groups in each habitat, but their proportion in different habitats were difference. There are great differences in the ingredient and common groups of soil arthropod communities among each habitat. There are more tropical characteristics for soil arthropod communities in the tropical monsoon rainforest than that in the tropical montane rainforest. The distribution of groups, individuals and important genera (the density1 000·m-2)of soil arthropods in the tropical montane rainforest (22 order, 4 974 individuals) are higher than those in the tropical monsoon rainforest (19 order, 1 632 individuals). The character of vertical distribution is that the individuals and groups of soil arthropods on the ground are more than those in the soil. There are difference between the Shannon Wienner diversity indexes and DG index of soil arthropod communities structure in two different tropical rain forests. Because of dominant group (Acari)individuals is larger in the tropical montane rainforest, it has the J, H' indexes of soil arthropod community in the tropical montane rainforest decreased, and it is less than that in tropical monsoon rainforest. The DG index are proposed on the base of the hypothesis that every species has equal independence and importance in the community, and can be compared with in community. So it is good to use DG index to measure the complicated soil arthropod community diversity. The results show that the richness and DG indexes in the tropical montane rainforest are much higher than those in tropical monsoon rainforest. It is positively related with the contents of soil organic matter and total N.