Abstract: Numerical simulation was carried out to investigate into shock-induced detonation initiation of the premixed H2/O2/N2 gas mixture in a duct with multi rectangular-shaped obstacles. Numerical results show that even if incident shock is not strong enough to induce the direct initiation of combustible gas mixture behind the shock front, the onset of detonation may take place in the cavity between obstacles where is far behind the shock front. Compression wave, expansion wave and shear layer generated from the surface of obstacles play important roles on chemical reaction that triggers the DDT process of detonation. Increasing N2 dilution of combustible gas mixture will influence the profile of wall temperature behind detonation wave and varying the distance between obstacles will results in the changes in the position of detonation initiation.Key words：Detonation initiation, multi-obstacle, cavities in wall