Abstract: A schematic configuration of dual-step supersonic combustor was proposed to overcome the high gasdynamic drag of scramjet engine in high-Mach-number flight (Ma ≥ 7). Numerical simulations were conducted to evaluate the coupled mixing and combustion features of fuel jet and dual-step flowfield. A scramjet model with dual-step was designed and tested in the JF12 Shock Tunnel, which can provide the pure air medium for simulating high-Mach-number scramjet tests. During the 100 ms test duration of JF12 Shock Tunnel, successful ignition and stable combustion of hydrogen-fueled scramjet models were realized in both simulation conditions of Ma=7.0 and Ma=9.5 and the experimental results were compared. In the simulation condition of Mach 7, three-dimensional inlet was used and the entrance Mach number of supersonic chamber was about Ma_c=2.5. The wall pressure distributions showed that the combustion took place in the upstream of expansion section of duct. In the simulation condition of Mach 9.5, two-dimensional inlet was used and the entrance Mach number of supersonic chamber was about Ma_c=3.5. The combustion took place near the exit of inner duct of scramjet model.