Abstract: Geometridae is one of the three big families in Jianfengling, Hainan Island. At present, more than 440 species had been collected and 126 subspecies and species belonging to 87 genera had been identified. Among them, five genera of Comibaena, Luxiaria, Semiothisa, Tanaorhinus and Terpna are dominant and 16 species of Clear a determinate, Fascellina chromataria, Hemerophila subplagiata and the others are of dominant species. As compared with other families of the moths, much more population densities are found in Geometridae according to the moth-killing lamp collection, their ecological distributions in the four forest types are found to have the most in species quantities in the tropical mountain rain forest. The adults occur in April and May having the most in species but the appearances of the population quantities are the most in January and May.