Aeolian deposition in the central north Pacific has been well recognized to originate from arid Asian interior. However, works on terrestrial organic tracers therein are rare. In this work, higher plant leaf wax n-alkanes from ODP Site 1208 in the northwest Pacific since the middle Miocene were analyzed to explore the source region vegetation and climate changes. Both average chain length of wax n-alkanes and their accumulation rates showed a general increasing trend, consistent with the well recognized climatic drying trend of the Asian interior. The record of isotopic fractionation factor between plant and atmospheric CO (sub 2) (epsilon (sub plant-CO2) ), calculated from delta (super 13) C values of n-alkane and atmospheric CO (sub 2) , showed a prominent decrease from 12.4 to 9.3 Ma, and displayed a general pattern of higher values prior approximately 8 Ma and lower values post approximately 8 Ma. Although all values of epsilon (sub plant-CO2) (-18.5 to -16.8 ppm) were well within the range of C (sub 3) plants, adjustment of isotopic discrimination of C (sub 3) plants was rule out as the main cause of the observed epsilon (sub plant-CO2) variations. Therefore, relative abundances of C (sub 3) vs. C (sub 4) plants were invoked to interpret the epsilon (sub plant-CO2) record, and higher C (sub 4) contributions (13.8 + or - 2.0%) were inferred due to slightly warmer climate in the source region prior to approximately 8 Ma. The suggested major C (sub 4) decline from 12.4 to 9.3 Ma was concurrent with evidences supporting a prominent uplift of northern Tibetan plateau [1], demonstrating close relationships of Tibetan uplift, drying and cooling climates, and vegetation changes of the Asian interior.