The spatiotemporal distribution pattern of the rice leaf rollers was analyzed and the atmospheric circulation background in which the typical immigration process happened were studied. The model of FLEXPARTWRF was used to speculate the immigration path in order to illustrate the influence of atmospheric background on the path. The research results showed that (1) the bimodal type was the major type of the rice leaf rollers in 2008 and the most extensive serious immigration process was during the period from 15 to 18 July. (2) The representative station Huaiyin in Jiangsu Province was chosen to simulate the source by FLEXPART, and the immigration of the rice leaf rollers was from the middle of Jiangsu and the midwest of Anhui Province. (3) The synoptic situation including the distribution, movement and strength changes of weather system at 850 hPa isobaric surface played important transferring and controlling roles on the migration and landing of the rice leaf roller. The prevailing deflectednorthward wind at 850 hPa isobaric surface was favorable for the northward migration of rice leaf roller. However, the prevailing deflectedsouthward wind at this height had no obvious influence on the southward migration. The zones with anticyclonic circulation in the wind field at 850 hPa isobaric surface were beneficial to the immigration and landing of the pest, and the cyclonic shear was beneficial to the emigrating of the pest. (4) The rainfall in the migrating paths of the rice leaf rollers played a critical role in the intensive landings of the pest.