Abstract: In order to achieve successful transition of detonation wave from the pre-detonator to main detonation tube,numerical simulation was performed for the exits of different geometry shapes,and the diffraction characteristics of detonation wave were obtained from pre-detonator to main tube.The results show that when the pre-detonator has a straight nozzle,the detonation waves cannot propagate upstream from the interface between the main combustor and pre-detonator exit;when the pre-detonator exit has a 45-degree nozzle,the detonation wave can diffract to both sides in main combustor.These results have been proved by laboratory experiments.