Abstract: The two-dimensional plane shock wave focusing with the parabolicreflectors in combustive gases is numerically simulated, and the ignitioncharacteristics of the detonation initiation are investigated. In thestoichiometric hydrogen/air mixtures under 20\,kPa, the shock wave focusing withthe incident Mach number 2.6\sim2.8 will generate two ignition zones. One isderived from the reflection shock convergence; the other is derived fromthe high temperature zone, which is induced by Mach Reflection on theparabolic reflectors. Then the focusing shock wave with the incident Mach number2.6\sim2.8 will induce the detonation initiation via deflagration-to-detonationtransition. The initiation points locate on the tube wall, the parabolicreflector and near the second ignition point, separately. The correspondinginitiation mechanisms are the shock wave reflection on the tube wall, the shockreflection on the parabolic reflector, and the interaction of theignition-induced shock and the deflagration induced by the second ignitionzone, respectively. Different ignition and detonation initiation processesresult in various wave systems in the flow field, and lead to different wavedynamic processes of the detonation wave propagation.