Abstract: To investigate the characteristics of the complex wave systemoutside a multi-tube pulse detonation engine, the space-time conservationelement and solution element(CE/SE) method was used to simulate theflow-field inside and outside the pulse detonation engine with seven tubes. Onetube was in the center, and the other six were around it in a ring. All seventubes were filled with the stoichiometric hydrogen-oxygen mixture. Theresults of calculation show that this CE/SE method can capture the shocks efficiently; there are severalinteracting or impacting shocks and expansion waves outside the 7-tubepulse detonation engine. The results of calculation can be used to study the characteristics of flow-field outside the multi-tube pulsedetonation engine.