Propylea japonica is small ladybug(approximately 4-5mm) and is met with everywhere in Korea. When there was no aphid, the survival rate of P. japonica was 0% among another instar bugs and 26.7～32.8% among same instar bugs after 48 hours. When there were sufficient aphids, the cannibalism of P. japonica was low, so the survival rate of P. japonica was 78.6～95.8% among another instar bugs and 80.6～100% among same instar bugs after 48 hours. In the comparison of the number of eggs at different oviposition site, P. japonica preferred the corrugated cardboard. In experiment using T-tube, the rate of decoy was 81% at cotton aphid compared with pepper leaf and 62% at cotton aphid compared with artificial diet. In the artificial diet using shrimp and chicken liver, the developmental period from egg to adult was 17days and the survival rate from egg to adult was 66.7% but the vitality was not good. These data suggest that P. japonica can be used effective natural enemy for control of aphids and is needed to research about artificial diet, mass rearing system and control effect in field.