Abstract: Numerical simulations of the complicated flow field of an unsteady supersonic ejector have been performed with the use of two-dimensional, homogeneous and reactive Euler equations, and the combination of the high resolution hybrid Roe/HLL scheme with AMR (Adaptive Mesh Refinement) technology. Simulation results described the processes of both the shock wave propagation inside the ejector, and the secondary detonation wave inside the ejector induced by the reflection of shock waves. The ejecting mechanism of supersonic unsteady ejector has been discussed, which can provide important guidance for further investigations on the unsteady ejector and its engineering equipment design in future.