The Cenozoic strata of the Zanda basin in southern Tibet have yielded abundant ostracoda fossils.Two ostracoda assemblages have been established based on the distribution patterns of the ostracoda fauna on the stratigraphic profile: ① Ilyocypris bradyi- Cyclocypris orum- Leucocythere dorsotuberosa assemblage；and ② Leucocytherella- Candoniella zadaensis- Leucocythere mirabilis assemblage. Through comparison of the ostracod assemblages of the study area with those found worldwide at the same stratum, the age of the Tuolin Formation in Zanda basin has been redefined to late Miocene to Pliocene.Based on the distribution characteristics of the fossil succession, the ostracoda fauna in the study area has been be divided into seven ostracoda communities in ascending order: Candona- Candoniella community；Ilyocypris- Cyclocypris community；Leucocythere- Candona community；Ilyocypris- Leucocythere community；Leucocythere- Leucocytherella- Candona community；Leucocythere mirabilis- Candona community and Ilyocypris- Leucocytherella community.Through detailed character analysis of ostracod communities and the magnetostratigraphic chronological data, the paleoclimate of the Zanda basin during 9.5~1.7 Ma was divided into six periods: ① the cool and wet period (9.5~8.4 Ma)；② the warm and humid period (8.4~6.3 Ma); ③ the cool and wet period (6.3~5.5 Ma); ④ the warm and humid period (5.5~4.4 Ma); ⑤ the cold and wet period (4.4~2.8 Ma); and ⑥ the warm and dry period (2.8~1.7 Ma).Through a comparison of the climate evolution characteristics of the study area with the global climate evolution since 9.5 Ma, it is postulated that the Zanda basin experienced primarily warm and humid conditions between 9.5 Ma and 6.3 Ma, likely related to the strengthening of the southeast monsoon from India.The paleoclimate analysis of the Zanda basin during the interval 6.3~3.6 Ma indicates a relatively warm and humid period, with climate fluctuations, possibly due to the re- strengthening of the southeast monsoon from the Indian Ocean.Subsequently, after 3.6 Ma, the influence of the global climate cooling, winter monsoon strengthening, and the strong uplift of the Qinghai Tibet Plateau caused a shift towards a cold and dry environment in the Zanda basin.However, the area experienced a transition to a warm and humid climate between 2.8 Ma and 1.7 Ma.