Abstract: The HyTRV (Hypersonic Transition Research Vehicle) is designed for the study of hypersonic complex three-dimensional boundary layer transition, the shape of which is close to that of the real aircraft. The principal objective of this research is to gain deeper understanding of the stability characteristics and transition mechanism of the boundary layer over the HyTRV model and verify the results of numerical simulation and theoretical analysis. In the Mach 6 wind tunnel, the transition front and unstable wave evolution characteristics at the bottom of the HyTRV model, obtained by the infrared thermal imaging technology and high-frequency pressure sensors respectively, were compared with the results of one-dimensional stability analysis. At the angle of attack of 2 degrees, the instability crossflow region on the windward side, which is located after the front of transition at the centerline, shrinks and moves backwards compared to the results with zero angle of attack. Broadband high-frequency signals, containing multiple disturbances in different frequency bands, were found in the crossflow region. The interaction between various disturbances widens the frequency spectrum. Then the boundary layer appears to breakdown. The signal amplitude reaches saturation before the transition is complete.