Abstract: The species diversity status of important pollination insects , Bombus (Hymenoptera) was investigated at three sites , Mengla County at low elevations , Nanjian County at intermediate elevations , and Deqin County at high elevations , in Lancang River Basin in Yunnan , China. The species diversity of Bombus at present (1996～1980) and 20 years ago (1976～1980) was compared. The reduction of vegetation induced by human activities has led to great changes in the habitats , number of species and population size of bumble bees over 20 years. The changing tendency among pollination insect species and populations obviously varied due to different biological and ecological characteristics. The decreasing rate of endemic bumble bee species and populations is more rapid than that of common and euryecic ones. The results showed that changes of habitats induced by human activities significantly influenced species diversity of pollination insects in Lancang River Basin. To conserve and restore the population of bumble bees , the priority is to conserve and restore local ecosystems.