Abstract: Was the living environment of the Yuanmou hominoid forest grassland, savanna or dense forest? Was the climate cool and dry, or was it warm and humid? This article analyzes the abundant data on plant fossils and palynology in six representative Miocene sedimentary basins. The results indicate that during Miocene Epoch there was widespread distribution of tropical or subtropical evergreen broad-leaf forest or mixed deciduous-evergreen broad-leaf forest in Yunnan. The climate during that time was warm and humid. During the period of the latest Miocene, the distribution areas of deciduous broad-leaf forest and conifer forest expanded at which time the climate became cool and dry. The Lufeng hominoid, a neighboring locality of the Yuanmou hominoid，experienced the same environmental change. Therefore, the living environment of the Yuanmou hominoid was a dense forest with a warm and humid climate. Other issues regarding this environmental analysis can be found in the book Yuanmou Hominoid.

Key words: Miocene; Natural environment; Yuanmou hominoid; Yunnan