The Tien Shan is one of the most active intracontinental orogenic belts worldwide and shows intensive seismicity and tectonic activity that reflects laterally heterogeneous structures. Here, we employ multimode surface wave tomography to construct an anisotropic 3-D shear-wave velocity model, which achieves a resolution of 2.0°. The new tomographic model reveals pronounced velocity contrasts between the central Tien Shan, which shows low velocity, and the eastern Tien Shan, which shows high velocity in the depth range of 50–300 km. We interpret that this velocity contrast as potentially resulting from the difference in the uplift mechanism of the Tien Shan. A comprehensive analysis suggested that the uplift of the central Tien Shan might be related to northward subduction of the Tarim lithosphere while the low-velocity anomaly beneath the central Tien Shan might be related to subsequent mantle upwelling. In contrast, the Tarim block in the south collided with the Junggar Basin in the north, which may have led to the uplift of the eastern Tien Shan. The Tarim Basin is mainly characterized by high-velocity anomalies of SV waves but low-velocity anomalies of SH waves beneath the western Tarim Basin, which may be related to the Tarim mantle plume.