Rice leaf roller, Cnaphalocrocis medinalis Guenee, is one of the most important crop pests in China due to its large area of occurrence, high frequency of outbreaks and serious damage to rice yields. In this paper, the lighting trap observational data of rice leaf rollers from 2000 to 2012 were analyzed to assess the impacts of atmospheric conditions on the migration and landfall of rice leaf roller. We have identified the main features of rice leaf roller's migration in the main rice-growing areas of China and presented a detailed analysis on a typical migration event occurred in late July, 2007 and verified the assessment result. By means of the Hybrid Single Particle Lagrangian Integrated Trojectory Model for Version 4.0 (HYSPLIT-4), a software of calculating particle trajectory in the air, the backward migration trajectories of the rice leaf roller landfalled the rice growing regions in the the Yangtze River Valley were calculated and the Weather Research and Forecast model (WRF) 's simulations on the atmospheric backgrounds in this event combined with the reanalysis data of the National Ceter of Environmental Predicting (NCEP) were used to assess the impacts of weather conditions on the catastrophic migrations of rice leaf roller. Several important findings are obtained from this study. First, during the studying period from 2000 to 2012, the migration of rice leaf roller started at the beginning of March in a year, the period during March to August was the period of prevailing migration northward in which the populations immigrate into the south China, the southwest China, the regions between the Nanling Mountain and the Yangtze River and the valley regions between the Yangtze River and the Huaihe River in China successively and emerge a series of immigration peaks. During the period from September to November each year, the southward migration is the reversed processes in the above regions. The rice leaf roller migrated backward to the valley region between the Yangtze River and the Huaihe River, the regions between the Nanling Mountain and the Yangtze River and South China in turn. Second, the backward trajectories calculations of rice leaf roller's migration northward included the beginning and re-emigrating populations in the selected event indicated that the sources of the rice leaf roller's populations were situated at the southwest parts of the landfall regions and the migration altitudes varied from 550 m to 850 m above ground level. As a comparison, the migrating trajectories in the coastal regions were more complicated than the other regions. Third, the horizontal wind is the main driving force for the long-distance migration of rice leaf roller's populations and the prevailing southerly at 925 hPa height is favorable for the migration northward. Three-dimensional windfield, especially the strong vertical airstream plays a dominant role in the up and down of the migration heights. Fourth, the downward flow and rainfall are the two key dynamic factors for the landfall of the rice leaf rollers. Fifth, as a kind of hygrotaxis pest, the suitable atmospheric moisture condition is beneficial to the long-distance migration and landfalling of rice leaf roller's populations. In this event, most of the rice leaf rollers landfalled in the areas of the relative humidity higher than 75%.