Rice stem borer, Chilo suppressalis Walker is a significant rice insect pest. A newly hatched larva bores a hole into the rice stem and feeding inside. The damage results in drying and white heads of rice. Climate change will affect pest and its host population dynamics variously. In this study, the degree of asynchrony between emergence of rice stem borer and rice transplanting was examined by their phenology models. Also, correlation was examined between winter mortalities of the rice stem borer and relative humidity categorized by daily minimum temperature in 12 sites throughout the country from 1992 to 2013. The degree of asynchrony appears to be increased in future climate condition. And we found a negative correlation between winter mortality and the relative humidity. Winter mortality will be decreased in the future because of increasing winter minimum temperature and snowfall. We hypothesize that the stem borer may increasingly harbor in alternative hosts such as reed in its first generation and move to rice in the second generation. Currently the simulation study is being conducted to verify this hypothesis.