The effects of X-ray irradiation on development and reproduction of Spodoptera litura were examined. Eggs, larvae, pupae, and adults were irradiated at target doses of 10 - 250 Gy. When eggs were irradiated with 30 Gy, egg hatching was completely inhibited. When irradiated to the larvae, pupation was inhibited at 100 Gy and larval period was delayed. When irradiated to the pupae, emergence was inhibited at over 100 Gy. When irradiated to the adults, longevity and fecundity did not show any differences. However, egg hatching was significantly decreased at 70 Gy and above. Also, X-ray irradiation was not induced the rapid death of S. litura. Reciprocal crosses between irradiated and unirradiated moths demonstrated that males were more radiotolerant than females. The levels of DNA damage in S. litura adults were evaluated using the alkaline comet assay. Our results indicate that X-ray irradiation increased levels of DNA damage. The recovery of DNA damage in S. litura adults increased as time passed. But DNA damage hasn't recovered fully. These results indicate that X-ray irradiation induced abnormal development and reproduction by DNA damage in S. litura.