Mythimna separata (Walker) moths captured in light-traps were monitored in Luohe, central-northern China, from 1980 to 2016. Annual average temperature recorded an increase of 0.298 oC/10 years in this region in the period. Our results indicate that a rising Apr and May avarage temprature and earlier occurrences of days recording the highest day temperature (30℃) caused an advanced peak and increasing proportion of high ovarian development levels of first generation females in earlier summers. Results using Johnson’s formulation of ‘oogenesis-flight syndrome’ indicate that increasing sexual maturity proportion has resulted in more emigrant individuals in the local first generaton moth becoming residents, and then increased individuls repidly in the local second generation moth since 2006. Consequences of this action have a boom in corn damage since 2007 in this region. Advanced peak dates of the first and second generation moth revealed the same response to increasing average monthly temperatures in the monitoring period. Increasing temperatures, the avarage May temperature exceeds or equal to 22℃, during the early 2000's may represent a physiological threshold for M. separata development. Our results suggest that climate warming may impact M. separata migratory status and cause a problem of crop production in this region.