plenty of geophysical data have been recently obtained in Qinghai-Tibet region, including the results of Sino-French joint study conducted in 1980-1982. The Qinghai-Tibet plateau is a unified geological element and may be divided into three belts according to its structural activities:the center is a uniformly uplifted block in isostatic status, while the northern and southern margins, having been subjected to intense compression and overlapping, are differential uplifts not yet reaching an isostasy. Its structural forms consist of three stru ctural layers with the upper (upper crust) dominated mainly by overlapping, the middle (lower crust) by compression, and the lower (anomalous mantle) by uplifting. An intracrustal layer of low-velocity and low-resistivity exists between the upper and lower crust, being a major sliding plane. The geological evolution of this plateau might have experienced two stages: before the collision between Indian and Tibetan plates, buoyancy of the anomalous mantle caused the pla teau to uplift gently;after the collision, the crust thickened and the plateau uplifted rapidly owing to the isostasy.