Abstract: Fall army worm (FAW), Spodoptera frugiperda is a major agricultural migratory pest worldwide, and migration is the key reason for the widespread damage which was profoundly affected by the topography. The specific ecological effect of river valleys on the migration of FAW in Yunnan was studied, and the results showed that: ① The longitudinal valley, as a typical ecological corridor, has a significant channel effect on the migration of FAW from south to North. ② The mountains on both sides of the valley hindered the crosswise spread of FAW, forming an obvious physical barrier. ③ The higher heat accumulation in the low altitude area of the valley provides overwintering sites of FAW, showing an obvious convergence effect. It is concluded taht the topography of the river valley has some specific ecological effects, which caused by the comprehensive impacts originated from temperature, airflow, and corn planting in valley, and the ecological effects had far-reaching influence on the migration and spatiotemporal distribution of FAW in Yunnan. This study has important guiding value for the regional control of FAW in Yunnan as it brings forward targeted control strategies based on the occurrence and development process of FAW in different river valleys.