Regional aeromagnetic survey, regional gravity reconnaissance and observa tion and analysis of modern seismic activities all indicate that the Qinghai-Xizang plateau is a quite peculiar and young structural unit of great size. It is characterized by thin magnetic crust, lenticular crustal structure and block as well as mosaic structures. Intense thermal flow and seismic activities, strongly decaying geomagnetic fields and isostatic gravity anomalies large in area reveal that at present the Qinghai-Xizang plateau is still in the process of temperature -rising, upwarping and napping.Low-velocity and low-resistance layers aer ubiquitous within the crust of the Qinghai-Xizang Plateau, and there develop crust-mantle mixed layers beneath the crust. These layers divide the crust into two types of structures with different characteristics. The upper crust is noted for dislocation, superimposition, napping and thickening, while the lenticular layer has been formed in the lower crust as a result of the addition of and mixing with large quantities of materials from upper mantle and asthenosphere. The isostatic state of the lithosphere is wrecked by compression, napping and superimposition of the crust, whereas the development of the crust-mantle mixed layer serves as compensation and adju stment for the nonisostatic state of the crust and the mantle.On account of the high temperature and high pressure environment preva iling at the depth of the crust as well as the transformation and rosorption of the paleostructural and paleolithofacies features, the geophysical characteristics observed today represent mainly the recently-developed and the remaining structural features.The Qinghai-Xizang plateau attributes its formation to the collision and suturation of two continental plates different in evolutionary history. Aeroma-gnetic survey and other geophysicel survey suggest that the combination belt between the two large plates seems along the Jinsha River-Hong River fracture zone and, somewhat to the south of it, the Tanggula-Sanjiang structural zone. The two sides of these zones are evidently different in background of regional magnetic fields.