The Saishiteng Mountain, located in the convergent part of North Qaidam tectonic belt and Altyn Tagh fault zone, belongs to one part of the North Qaidam tectonic belts. Granitic pluton outcropping in this area has long been regarded to form in early Mesozoic and should be the granitic rock resulting from the early Mesozoic ocean- continent collision. This study investigated the two grantic plutons in Saishiteng Mountain using LA- ICP- MS zircon U- Pb dating, Lu- Hf isotopic and trace element analysis. The results show that three granite samples from the two plutons have zircon U- Pb ages of 260±3Ma, 268±8Ma and 263±8Ma, respectively, indicating that they formed in the Middle Permian, but not previously suggested early Mesozoic. 176Hf/177Hf values of all zircons range from 0.28294 to 0.28320, with extremely high positive εHf value of 11 to 20, and average two- stage model age of 350 Ma, higher than U- Pb age, suggesting that source region might be characterized by new- born mafic material with feature of depleted mantle. Combined with regional geological characteristics and existing research results, this study concludes that the Middle Permian granite with high positive εHf values might form from patial melting of Middle Permian subduction of oceanic crust due to the extension of the Zongwulong oceanic basin westward to Saishiteng Mountain area. The discovery indicates that oceanic plate subduction occurred in the Permian, which provides new evidence for understanding the Late Paleozoic- Mesozoic tectonic evolution in the northern Qaidam Basin.