Basic sill swarms of two periods were found in Lalongwa and Manzhanggang in the southeastern part of the secondary orogenic belt on the eastern margin of the Qaidam basin in the junction area of the Western Qinling and Eastern Kunlun orogenic belt. Their 40Ar/39Ar ages are 393. 5 Ma and 197. 5 Ma. The former was formed in the early period when the northern Paleo-Tethys and the Gonghe aulacogen between the western Qinling Mountains and eastern Kunlun Mountains began to be formed, whereas the latter marked extensional orogenic collapse after the tectonic system closed and collided to form an orogene. Comprehensive studies show that in the middle-late Paleozoic, when the rift from the southern Eastern Kunlun Mountains to A'nymaquen and the rift from A'nymaquen via Wenxian to Mianlue grew into an ocean, namely the northern branch of the Eastern Paleo-Tethys, the rift from Kuhai to Sertang between the Eastern Kunlun and Western Qinling Mountains failed and became the Gonghe Aulacogen. In the late Triassic, this tectonic system began to contract, close and collide to build mountains. Then the northern Eastern Paleo-Tethys was subducted under the Qaidam and Western Qinling terranes and collided to form the Qinling-Kunlun orogenic belt. The Western Qinling and Eastern Kunlun were finally joined laterally due to the closing of the Gonghe aulacogen. This research would provide evidence for the timing of the dynamic evolution of the Western Qinling and Eastern Kunlun Mountains and their junction.