Abstract: The earliest undoubted fossils of Quercus L. are not found until Eocene, although the oaks may have originated prior to the late Cretaceous. Most oak species from the old Tertiary rocks, which are assumed to be evergreen and ranged the montane tropics and montane subtropics near the sea ,can scarcely be referred to modern species. Both diversity of oaks and their dominance in flora increased in Oligocene and gradually reached their prosperous stage. In Miocene,there many existed extinct species groups and many essentially modern species were present. The oak distribuiion pattern in Pliocene was similar to modern one. The first deciduous oak species appeared in the middle Oligocene in Northeast China when the oaks in high latitude retreated southward caused by the spreading of colder and drier climate. In early Neogene oaks disappeared in Northwest China because of the occurrence of the Middle Asian Desert. Meanwhile, the species of Sects. Suber and Englerianae evolved in Southwest China as a result of orogenesis of the Mountain Himalaya. The fossil records indicated that the interchange of oaks between North America and China was not ended until the middle Miocene,while the linkage between Europe and China was not ended until the early Pliocene.

Key words: Quercus , Tertiary