Abstract: The effect of gamma irradiation on the growth and development of Tetranychus cinnabarinus was studied and a series of gamma radiation doses ranging from 95 to 1 650 Gy were treated on the eggs， nymphs and female adults. The results showed irradiation doses between 250 and 1 650 Gy could obviously affect the growth and development of their eggs， nymphs and female adults. A treatment of 330 Gy irradiation prevented eggs from hatching. Although an irradiation dose of 330 Gy could not directly kill nymphs and female adults within 3 days， it could make nymphs and female adult completely infertile and prevent their reproduction. An irradiation rate of 330 Gy is suggested as the minimum dose （Dmin） for phytosanitary measure.

Key words: Tetranychus cinnabarinus, irradiation as a phytosanitary measure, growth and development, minimum dose（Dmin）