The changes in the performance of an air-breathing pulse detonation engine resulting from the addition of a nozzle at the end of the constant area detonation tube were investigated using multi-cycle detonation experiments. Average thrust histories were computed for air-breathing PDE at five different operation frequencies with different nozzles. The area ratio and length-diameter ratio of nozzles effects on the average thrust were investigated. Seven different area ratios were used to find out the area ratio effect of nozzle on the PDE performance and three different length-diameter ratios were utilized to find out the length-diameter ratio effect. The results indicated that nozzles with area ratio less than 1 increased the average thrust distinctly at all operation frequencies compared with area ratio 1. As the area ratio decreased, the thrust augmentation increased and the highest augmentation ratio attained 32%. Meanwhile, the divergent nozzles whose area ratio bigger than 1 increased the average thrust slightly or even decreased the average thrust at most of the cases. And the performance of convergent-divergent nozzle was less than that of convergent nozzle with the same area ratio. The experiment data suggested that the lengthdiameter ratio of nozzle had little effect on the PDE performance and the average thrust decreased slightly with the increasing length-diameter ratio.