Abstract: By comparing the synthetic and observed seismic triplications for two events from Qinghai and Myanmar Arc with the trial-and-error method, the velocity structures of P-wave and S-wave from Moho to the depth of 180 km are obtained. The P-wave velocity models for the profiles A and B beneath Songpan-Garze block are 5% higher than that in the model C2AK, which is based on the model AK135 with crust structure of Crust2.0. The P-wave velocity model for the profile C beneath Sichuan-Yunnan block, however, is 5% lower than that in the model C2AK at Moho depth, and then increases slowly down to the depth of 120 km. The S-wave velocity model beneath Songpan-Garze block is 3% higher than the model C2AK from Moho to 180 km. Such regional difference in velocity structure may indicate that the lithospheric mantle beneath Sichuan-Yunnan block has been extruded more obviously than that beneath Songpan-Garze block in the uplift of the Tibetan Plateau.