Abstract: Considering the oscillatory flow in a pulse detonation engine (PDE), its plug-in-convergent-divergent nozzle was designed, tested and analyzed to improve the thrust of the pulse detonation rocket engines (PDREs). The plug-in-convergent-divergent nozzle is found to be effective for improving the propulsive performance of a PDRE, with 32.4% and 29.52% thrust augmentation for a PDRE at 10 Hz and 15 Hz, respectively. It is also found that the divergent part of a nozzle can utilize the potential capacity of exhaust gas at high temperature and pressure by accelerating the flow gas produced from the detonation chamber of a PDRE. In addition, the plug in the nozzle is demonstrated to be capable of keeping a high pressure at thrust wall, and making thrust augmentation possible for a PDRE by using the plug-in-convergent-divergent nozzle.