Doppler Insect Monitoring Radar (DIMR) observations of rice leaf roller Cnaphalocrocis medinalis migration were made at Pukou district of Nanjing from July to September 2007. Radar observations showed that large numbers of rice leaf roller moths migrated from dusk (18:00 h) until about 05:00 h the following morning. The maximum aerial density of moths usually appeared between 20:00 and 22:00 every night. The moths mainly flew below 500 m. The majority of the migrating moths on any one night usually aggregated in layers between 100 m and 500 m above ground, and sometimes two moth layers were present simultaneously, one above the other. The stratification of moth density was closely related to the low-level nocturnal jet rather than air temperature. We analyzed the migration dynamics and the temperature and wind profiles on the migration routes by numerical simulation using NCAR re-analysis meteorological data, the DIMR data and field survey data. The results showed that there were four migrations of the 4th generation of the moth in Pukou. (1) The moths immigrated from the southern area of Jiangsu on the peripheral wind field of a Typhoon on 18-19 August. (2) A large proportion of the moths in the local area emigrated to regions to the northwest on the low-level jet on the night of 24 August. (3) Another population immigrated from areas to the southeast of Nanjing on the following night, and (4) in early September, after one cyclone moving into the East China Sea, the rice leaf rollers in Pukou engaged in southwards ‘return’ migration on the northeast winds following the cyclone. Results indicated that the two massive immigration peaks of the rice leaf roller on the night of 18-19 and 25 August were associated with the subsidence around the low pressure system.