Abstract:This inverstigation, as a part of the plant and animal survey in the project on tropical forest ecosystem in Jianfenling mountain, Hainan Island, was conducted in 1981—1983. About 4000 insects have been collected, of which the Lepidoptera accounts for 50% and the Coleoptera and Diptera accounts for 13% and 11% respectively. The rest belongs to the other 17 orders. Take 26 families of moths for an example, the species of Noctuidae, Geometridae and Pyralidae are the dominant families, which accounts for 69% of the total collected moths. One character in population quantity is large in small population and small in large population. There are 17 dominant species, among which 10 species are in pyralidae, 4 species in Hypsidae, 2 species in Arctiidae and 1 species in Uraniidae. Most sp les of Acrdiidae and Pentatomidae have been found in tropical semidecidous monsoon forest and most species of Thrips and Moths in tropical mountainous rain forest. According to the composition of fauna, most species of Thripidae, Phlothripidae, Pentatomidae and Sphingidae are distributed in Oriental region. Some species local species in Hainan Island obtained are Antillothrips flavicornis Zhang, Dinothrips hainanensis Zhang, Agaeus tessellatus Dallas, Dabessus albovittatus Hsiao et Cheng and Rhagastis mongoliana pallicosta Mell. It may be concluded that the charateristics of tropical forest insects are abundant in species, less quantity for each species, more than one generation and no dormancy but diapause for widespread species.