Abstract: The Yinshan mountains is located in the interior of the eastern Asian continent and is mainly characterized by the exposure of a large area of the Early Precambrian, including the Neo−Archean and Paleo−Proterozoic metamorphosed complexes and late Paleozoic and Triassic plutons, and by multi−age thrusting tectonics with south− and north−verging movement. In the early publications, the mountains was considered as part of so−called Sino−Korean paraplatform, which is considered as same−meaning term with North China craton, implying its difference from the typical platform on the Earth. Since 1990’s, Mesozoic magmatism and structural deformation has been related to within−plate or intracontinental orogeny, and late Paleozoic magmatic rocks to the Andes−type of orogeny in the southern continental margin of the Paleo−Asian ocean between the North China in the south and Siberian platform in the north. However, the mountains have been still considered as part of North China Craton almost in all of publications, implying no change of its tectonic affinity. Whether the mountain is part of the craton or not, how it was changed from the Craton into the orogenic belt if it is not, is not only a regional or local tectonic issue, but also ones relating closely to the evolution of the continental dynamics, and deals with the scientific access of resource potentials. In this paper, the mountains is divided into three tectonic units based on available data both of magmatic rocks and structural deformation. The north unit is part of the island–arc type of an accreted orogenic belt adjacent to the northern margin of the ancient North China craton during the Early Paleozoic, the central one is an activated orogenic belt on the basis of and by the activation of the northern marginal part of the Craton from the Devonian to Triassic, and the south is part of an intracontinental activated orogenic one in the interior of the Craton in the period from the Jurassic to Early Cretaceous. It is further clearly stated that the central unit was changed from the craton into the orogenic belt by Devonian to Triassic magmatism and Permian to Triassic structural deformation, and that the south by two extension−compression tectonic cycles taken place in the period of the Jurassic and the Early Cretaceous, respectively. Then it is obtained the following conclusion that the mountains has lost its tectonic affinity of the craton since the late of the early Cretaceous and changed into part of a composite orogenic region which is composed by the western margin of the East Asian orogenic region and the southern part of the North Asian orogenic one. In the same time, it is the first time to publish some new data on structural deformation from those three units and put forward to some new viewpoints on the mountains i.e. that the the present geomorphological features of the mountains occurs in the late of the Cenozoic, that the area underwent four periods of crustal shortening events in the end of the Early Paleozoic, the latest of the Paleozoic, the late of the Jurassic and the late of the Early Cretaceous, respectively, that the central unit may be sub−divided into four sub−belts, that the three stages of structural deformation of Bayan Obo group sedimentary sequences are distinguishied into tight folding in the early one, and then the right−side strike−slip in the second, and northward thrusting in the third, and that the the timing of the intensely north−verging thrusting of the south unit is determined as the late of the Early Cretaceous. Lastly, some suggestions on the tectonic issue which remain to be further studied and investigated in the mountains, are briefly stated.