Abstract: Two-dimensional axisymmetric numerical simulation was carried out using single-cycle and detailed chemical reaction kinetics of hydrogen/air mixture,so as to investigate different nozzle effect on the performance of pulse detonation engines.The simulated results of detonation wave parameters are close to the value of a chemical equilibrium solver named STANJAN.The results of numerical simulation with four single-nozzles and four combined-nozzles indicate that,the largest instantaneous thrust and specific impulse are obtained in divergence nozzle;the average thrust generated by the combined-nozzle with ejector is larger than that by the single-nozzle.Furthermore,the mechanism of unsteady ejection was analyzed,offering references to augment the performance of pulse detonation engines.