Abstract: Pericyma cruegri (Butler) is an important defoliator of Peltophorum tonknense. It has 7 to 8 generations per year in Hainan Island. The adult likes to lay it's eggs on the forest floor of high terrain, forest fringe and the upper place or crown of the tree. It overwinters as pupa The larva las six instars. It's is likely that the pest would come in the rainy season, if the rain fall is less than the ordinary level in dry season. For chemical control, spraying the forest stock with 5ppm permethrin or 70% Carbaryl emulsion and 90% crystal Trichlorphon diluted with 2000—3000 times of water was found to be effective. To cultivate mixed forest and to lead Pericyma cruegri with lamp. Are recommended for the control of the pest.