Objectives: This study discusses the formation times, petrogenetic types, source rocks features and tectonic significance of the Oligocene granitoid rocks, which provide a geological foundation for the study of Oligocene intrusive rocks in the Gangdese belt and the uplift of the Tibetan plateau. Methods: On the basis of detailed field geological survey, LA- ICP- MS zircon U- Pb dating, Geochemistry and Hf isotope analysis. Results: The Oligocene granitoids of the study area consist primarily of granodiorite, biotite monzonite granite and porphyritic biotite monzonite granite, in central segment of Gangdese belt. LA- ICP- MS zircon U- Pb dating yield an age of (26. 6±0. 4) Ma for the porphyritic biotite monzonite granite, indicating that they were the product of Oligocene magmatism. The lithogeochemical characteristics of these rocks reveal a Rittmann Index (σ) of 1. 58~3. 20; they belong to the high- K calc- alkalic series and shoshonite series. The A/NK and A/CNK are 1. 14~1. 70 and 0. 90~1. 04, The rocks are enriched in large- ion lithophile elements (Rb, K), and depleted in Ba, Nb, Ta, Zr, Hf, Ti. The lithological and geochemical characteristics of granitoids indicate that they belong to I- type granite. The εHf(t) of zircon are from 0. 08 to 6. 31 of zircons from porphyritic biotite monzonite granite, and the single stage ages are from 445 to 687Ma. Conclusions: The Oligocene granitoids belong to I- type. In combination with the comprehensive analyses of the available data for the granitic rocks, it can conclud that the granitoids mainly derived from the partial melting of the new crust, and some from mantle- derived magma, The fractional crystallization during magma evolution are clearly identifiable. The gangdese belt was located in the tectonic enviroment of India—Asia collision, Compression and mantle emplacement caused the crust to thicken, it also leaded to the Tibet Plateau experienced a strong uplift during the Oligocene.