Abstract: Three Late Triassic plate sutures, namely, the Lungmu Co-Shuanghu suture, Kurdun-Qinling suture and Xijir Ulanjinsha River suture, have been recognized on the Qinghai-Tibet Plateau. Data show that the last two sutures have no essential elements of the northern boundary of Gondwana. This paper briefly introduces the basic fact of the existence of the PaleoTethys Ocean in the Lungmu Co-Shuanghu suture, i.e. the ages and natures of Early Paleozoic ophiolites, Permian ophiolites, Devonian-Permian radiolarian cherts, accretionary slabs of different natures, two types of tectonic mrlange zones and covers of ophiolites. The starting time of the Paleo-Tethys Ocean in Qiangtang may be traced back to Early Paleozoic and the records about the oceanic basin evolution persisted from the Late Devonian to Late Triassic. It is thought that the Lungmu Co-Shuanghu suture was the site for the extinction of the Paleo-Tethys Ocean on the Qinghai-Tibet Plateau and an important window for the reconstruction and inversion of the early-stage formation and evolution of the Qinghai-Tibet Plateau, as well as the northern boundary of Gondwana that the geoscience community has paid attention to in the past few decades.