Abstract: A parallel computation program for reactive flow was developed based on two-dimensional unstructured grid by adopting the modified CE/SE (space-time conservation element and solution element) method and parallel domain decomposition technology. The computational domain was decomposed into several sub-domains and the parallel computation was conducted by introducing the multi-tube PDE (pulsed detonation engine) with convergent-divergent nozzle. The processes of ignition in single tube and propagation in multi-tube were simulated for H2 and O2 under stoichiometric ratio conditions by using the 8-species, 34-elementary reaction model. Computed results demonstrate the followings: (1) the CE/SE method can capture the complicated detonation flow structures, and the conclusion in this paper agrees well with that in the literature; (2) detonation waves generated in single tube have significant influences on flow field structures of side-tubes and can ignite the fresh reactant in them.