Abstract: Research on hypersonic boundary layer transition is a hot topic in the field of aerodynamics in recent years. The flow stability of hypersonic boundary layer was experimentally studied by the Nano-tracer-based planar laser scattering (NPLS) technique and temperature-sensitive paints technique. Through the flow visualization experiments, the fine structure of the rope-like second mode wave in the conical boundary layer was measured, and the wavelength and frequency of the second mode wave were analyzed based on the temporal-correlated NPLS results. Compared with the boundary layer on the straight cone, the second mode wave on the flared cone is more obvious, and the evolution speed of the second mode wave is slower, so the fine second mode wave structure can be measured in a longer flow direction range. According to the NPLS results of flared-cone boundary layer, the spatial distribution results of power spectrum at specific positions were calculated, and the harmonic components were measured. Temperature-sensitive paints and flow visualization experiments indicated that the transition of the boundary layer near the edge of the delta wing was led by the traveling cross-flow mode, and the characteristics of this mode were consistent with the frequency measured by Kulite sensor.