The arbuscular mycorrhizal status of 112 plant species and the spore density of arbuscular mycorrhizal fungi (AMF) in the rhizosphere soil of these plants in the tropical rain forest of Xishuangbanna, southwest China, were surveyed. It was found that 56% of the surveyed species were arbuscular mycorrhizal, 31% were possibly arbuscular mycorrhizal and 13% were non-mycorrhizal. The spore density of AMF ranged from 55 to 1,908 per 100 g soil, with an average of 476. The rhizosphere soil from the arbuscular mycorrhizal plants did not always have a higher AMF spore density than that from the possibly mycorrhizal and non-mycorrhizal plants. The clumped distribution of AMF spores and the complex structure of the underground component of the tropical rain forest may be two important factors that affected the spore density of AMF. Fungi belonging to the genera Acaulospora and Glomus are the dominant AMF in the soil of the tropical rain forest of Xishuangbanna.