Based on the results of pure dispersions of Rayleigh wave tomography in the Qinghai-Tibet Plateau and its adjacent areas, taking S wave velocities from previous linear inversion as the initial model, us-ing the simulated annealing algorithm, a nonlinear simultaneous inversion has been carried out for S wave velocity and thickness of different layers, including the crust, the lithosphere and the astheno-sphere. The results indicate: The crustal thickness shows strong correlation with geology structures sketched by the sutures and major faults. The crust is very thick in the Qinghai-Tibet Plateau, varying from 60 km to 80 km. The lithospheric thickness in the Qinghai-Tibet Plateau is thinner (130―160 km) than its adjacent areas. And two blocks can be recognized, divided by an NNE strike boundary running between 90°E―92°E inside the plateau. Its asthenosphere is relatively thick, varies from 150 km to 230 km, and the thickest area is located in the western Qiangtang. India has a thinner crust (32―38 km), a thicker lithosphere of 190 km and a rather thin asthenosphere of only 60 km. Sichuan and Tarim basins have the crust thickness less than 50 km. Their lithospheres are thicker than the Qinghai-Tibet Plateau, and their asthenospheres are thinner. A discussion has been made on the character and formation mechanism of the typical crust-mantle transition zone in the western Qiangtang block.
