Abstract: A series of laboratory experiments was carried out to test the activities and histologicul changes of the benzoylphenyl urea(BPUs)chitin synthetase inhibitor dichlorbenzuron, against Asiatic apple leafminer, Lithocolletis ringoniella Mats. When the adults were fed continuously with sucrose solution containing 250mg/L dichlorbenzuron, the insecticide resulted in a higher infertility. Hatching rates of eggs and survival of the progeny were greatly reduced. Longevity of adults and mean numbers of eggs produced per female demonstrated no significant difference between dichlorbenzuron treated and control. Dichlorbenzuron had no direct effect on the eggs, but high activity to 1 instar larvae. Application at larvae stage in field, dichlorbenzuron could inhibit larvae development and pupate. There was no change in chorion and embryonic development, but the chemical could make the cuticle of the larvae in egg thin. The body wall layers of larvae were not clear comparing with the control and the cuticle was also thin and separated with epidermalcells. Shriveled basement membrane and thinned muscle layer in mid gut were observed. Dichlorbenzuron had good penetrability and long persistence on the leaves.