Qaidam Basin is located in the northern part of Qinghai—Xizang(Tibet) Plateau.Due to the influence of Qinghai—Xizang Plateau uplift and global climate,the paleoenvironment in the basin changed significantly during Neogene Period.Methods: Based on the analysis of the characteristics of palynology in the Yiliping Sag of Qaidam Basin,the Neogene vegetation types and environmental evolutionary process of the basin were restored,and the effects of plateau tectonic uplift and global climate change on the paleoenvironment of the basin were discussed. Results: The results show that the Neogene palynological assemblages in the Yiliping Sag is characterized by abundant gymnosperms,a lot of angiosperms and many xerophytes.Conclusions: The palynological characteristics indicate that the climate in the Yiliping Sag of Qaidam Basin belongs to semiarid or arid climate during the whole Neogene period,and the Neogene palaeo-environmental evolution was significantly affected by the uplift intensity of the Qinghai—Xizang Plateau and the global climate: the environments during the deposition of the Lower Youshashan Formation, Upper Youshashan Formation and Shizigou Formation are belonging to Subtropical forest,temperate forest—grassland and cold temperate grassland—semidesert, respectively.This environmental background of this period is not beneficial for the development of large-scale high-quality source rocks in the Yiliping Sag during Neogene Period.