Annotation:::: The paper provides a historical and ethnological view on migrants in Yunnan’s mountain areas, and aims to draw lessons from the past to inform the present work of eco-migration and development. Employing methods of documental and empirical study to analyse this migration, the author finds that, during the Qing dynasty, there was an upsurge of development in the mountain areas and lot of outsiders came into and settled down in these areas. Migrants took advantage of mountain areas of Yunnan, and helped to promote local ethnic integration and consolidate the frontier of southwest China. However, they also contributed to some problems in the areas at the same time, particularly in terms of population expansion, ecological concerns, and poverty. In the current context, lessons can be drawn from these historical occurrences to improve the present work of eco-migration and development.