[Objectives]  To clarify the source population and migration pattern of Spodoptera frugiperda migrating into Hainan province, and provide a scientific basis for predicting the presence of S. frugiperda in Hainan. [Methods]  Using data on S. frugiperda collected in Haikou city in 2019, the WRF three-dimensional, trajectory-analysis program, combined with the flight behavior parameters S. frugiperda and relevant meteorological data, were used to analyze the migratory path of this species in Hainan. Weather parameters during the migration were also simulated and analyzed. [Results]  S. frugiperda migrated into Hainan in 2019 mainly from the 15th to the 20th April. During this period, southwesterly winds in Vietnam and a low-level jet-stream in southern China provided the carrier airflow for the migration, whereas strong convection rainfall, wind shear and downdraft forced the landing of migrating insects. There was an effective flight path of S. frugiperda from the 15th to the 17th of April, which allowed it to invade Haikou city, Hainan province. The source population was in Vietnam and northern Guangdong. Subtropical high pressure, precipitation and wind patterns led to the migration of this population to Hainan. [Conclusion]  This preliminarily study has clarified the earliest migration of S. frugiperda in southern Hainan in 2019 and the source population for this migration.