The hypersonic boundary layer transition over a concave wall is investigated in a Mach 6.5 quiet wind tunnel using temperature sensitive paint (TSP), CO2-enhanced filtered Rayleigh scattering flow visualization, PCB fast-response pressure sensors, and a high-frequency schlieren technique. The TSP shows that low- and high-temperature streaks are distributed in the spanwise direction. The wavelengths of naturally developing Görtler streaks are randomly distributed, with an average of approximately 7 mm, and change little as the unit Reynolds number increases. More importantly, three-dimensional waves are clearly visualized and quantitatively measured inside the Görtler streaks. This is the first time that the entire evolution of the Görtler instability has been visualized using the Rayleigh-scattering flow visualization in hypersonic flow. The results demonstrate that three-dimensional waves are amplified as a result of the Görtler instability, resulting in a localized high-shear layer around the interface of the three-dimensional waves, which contributes to the formation of hairpin vortices and mushroom-like structures. The three-dimensional waves grow and play an important role in Görtler instability-induced boundary layer transitions.