Pulsed combustor, it has features such as taking out work without a compressor and mixing promotion by a complicated flow field. The purpose of my research is to evaluate the thrust of a pulse combustor that substitutes this check valve with an ejector mechanism without moving parts, and to clarify the pressure-gain of pulsed combustion and grasp the combustion state with pressure and visualization measurement. Although the total pressure of exhaust gas was lower than the oxygen plenum pressure in all shots, these were almost equal in case in which the pulse combustion was stably continued. It was also found that the expansion wave and the compression wave reciprocate in the combustion section, and that the behavior of the pressure wave and the flame were synchronized. A pulse combustion cycle due to this pressure wave reciprocation was estimated, and the sound velocity obtained from this was in agreement at the order level with theoretical value.