On 8 August 2017, an earthquake of the magnitude of Ms7.0 struck the Minshan area of the northeast Tibetan Plateau. Focal mechanisms of the main shock and the epicenter distribution of aftershocks, together with historic earthquakes and neotectonic analysis, clearly reveal a newly developing sinistral strike- slip fault, namely the Jiuzaigou- Huya fault. The fault obliquely cut the Minshan uplift zone, forming an arc- shaped zone. It is the easternmost extension of the East Kunlun sinister strike- slip faulting zone, linking to the Tazangcha fault in the north and the Huya fault in the north. The neotectonic studies show that the Bayan terrane in the eastern Qinghai- Tibet plateau extruded eastward and kinematic nature of the faults in the Minshan uplift zone has changed remarkably during the Quaternary. It was predominated by reverse faulting during the Early- Middle Pleistocene Kun- Huang Movement stage (ca.1~0.6Ma), which accommodated eastward extrusion of the Bayan Har Block. Since the late Late Pleistocene（ca 120 ka）, the terrane extruded eastward accompanied by clockwise rotation and tectonic deformation was dominated by sinistral strike- slip motion along the newly developed Jiuzaigou- Huya fault zone. Transition of the fault mechanism made some early active faults (such as the Minjiang fault, the Zhangzhai fault, etc.) less active and even dead at present, while new active faults are on the way. This evolutionary image of Quaternary faults may give a new insight into seismic assessment along the eastern margin of the Tibetan Plateau.