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The Tianshan orogenic belt is one of the youngest and highest inland orogenic belts in the world.In order to investigate the detailed structure of the crust and uppermost mantle of the eastern Tianshan,a 600km long seismic refraction/wide-angle-reflection was carried out along a geophysical profile extending northeastward from Korla at the northern margin of the Tarim basin,through the Tianshan orogenic belt,to Jimsar at the southern margin of the Junggar basin.By data acquisition and phase identification such seismic phases as Pg,P1,P2,P3,Pm and Pm′ have been obtained.The seismic data yield the P -wave velocity structures of the crust and uppermost mantle of the northern margin of the Tarim basin,the Tianshan orogenic belt and the southern margin of the Junggar basin through data processing and 2D ray tracing and theoretical seismogram calculation.We also obtained a 2D density structure and 2D magnetization intensity structure by joint inversion of gravity with geomagnetism.The velocity structure shows that the crust of the Tianshan is characterized by a greater average thickness and lower average velocity,compared with that of the Tarim basin and the Junggar basin.The Moho at the southern margin of the Junggar basin dips south to the Tianshan,suggesting a subduction of the Junggar basin to the Tianshan orogenic belt.The Moho at the northern margin of the Tarim basin is discontinuous,suggesting that the subduction of the Tarim basin to the Tianshan is rolling back due to the clockwise rotation of the Tarim basin.Located between the Tarim basin and the Junggar basin,the two rigid blocks with relatively high velocity,the Tianshan orogenic belt becomes a shortening zone under lateral compression.The subduction and rolling back model for the Tianshan orogenic belt revealed by the geophysical profile from Korla to Jimsar is quite different from that of another profile from Xayar to Burjing,which indicates that the Tarim basin subducts to the Tianshan orogenic belt,while the Junggar basin contacts the Tianshan in a pattern of strike sliding.The differences in the lithospheric structure of the Tianshan orogenic belt,especially its relation with the basins at its sides indicates that the Tianshan orogenic belt,which extends about 3000km,has different features at its different segments.