Rice striped stem borer (RSSB, Chilo suppressalis) is a serious lepidopteron pest occurring in rice ecosystems of Asia and Europe. Genetically modified (GM) insect-resistant Bt rice has been developed to deter lepidopteron pests including RSSB. The concern of resistance evolution to the Bt toxin by the pests under commercial cultivation of GM Bt rice and the need of effective management of the resistance encourage the studies of genetic variation and divergence, as well as gene flow of RSSB populations. We analyzed 13 RSSB populations fed on water-oats or rice plants, respectively, from southeast China applying the fluorescent amplified fragment length polymorphism fingerprints. A generally moderate level of genetic variation was detected in the populations, as estimated by Nei‘s genetic diversity (0.27) and Shannon‘s index (0.42). The FST and amova