<p>To investigate the typical unsteady structures and gas–solid coupling mechanisms in particle-laden transverse jets in high-enthalpy supersonic flows, a reliable experimental approach was developed and systematically validated. The experimental system consists of a high-enthalpy supersonic flow facility and a custom-designed particle injection device. It generates a Mach 2.63 (~ 1406 m/s) flow with a total temperature of ~ 1633 K, along with continuous and stable injection of SiO₂ particles ranging from 0.1 to 150 μm in diameter. A multimodal diagnostic strategy was employed to provide insights into the flow field. High-speed focused shadowgraphy captured the aggregation and sweeping–ejection processes of large-scale vortices acting on particle clusters. Planar laser scattering (PLS) revealed three representative particle distribution patterns—fluctuation, trailing, and roller type—as well as their quasi-periodic cascading evolution. Two-dimensional, two-component particle image velocimetry (2D–2C PIV) provided quantitative measurements of the particle velocity field. The results showed peak velocities up to ~ 1300 m/s and a pronounced non-monotonic stratification linked to particle inertia effects. These results demonstrate that the developed experimental platform and diagnostic methodology can reliably capture the complex unsteady features of particle-laden transverse jets in high-enthalpy supersonic flows. This provides a robust experimental basis and essential data for advancing the understanding of particle–turbulence mixing and transport mechanisms in high-speed flows.</p>