Cymbidium flower is mainly grown for exportation to China and Japan, but detection of a few pests including the cotton aphid, Aphis gossypii (Hemiptera: Aphidae), necessitated post-harvest treatment for casual exportation. Thus, we irradiated electron beam to cotton aphids occurring in cymbidium to establish post-harvest method for casual exportation of the flowers. For cymbidium, six categories of product quality were examined after eight different doses were irradiated (100, 200, 300, 400, 500, 600, 800 and 1,000 Gy). One thousand Gy to cymbidium caused an extreme deterioration only in vase life in both colors compared to control (0 Gy). In the case of cotton aphids, adult longevity decreased from 11.23 (100 Gy) to 4.70 (400 Gy) when four different doses were irradiated (100, 200, 300, and 400 Gy), with control being an average of 20.89 days. The numbers of total first instar nymph produced per adult was not significantly differed among five doses (2.21 ~ 2.74 individuals), but was substantially lower compared to control (an average of 51.46; P < 0.0001). Live F1 nymphs did not develope to adults at all five doses, except for a single nymph at 100 Gy, which was dead right after emergence. The results of probit analysis indicated that majority of adults required 3.33 ~ 7.55 days for 90% mortality at 200 Gy and higher, but at 100 Gy it required 41.56 days. Therefore, higher than 100 Gy might be required for complete control of adult cotton aphids and their F1.