The explosion behavior of syngas/air mixtures under the effect of N-2 and CO2 addition is experimentally investigated in three cases of N-2 and CO2 volume fractions (0, 20% and 40%). Tests are performed for syngas/air mixtures with varying equivalent ratios (from 0.8 to 2.5) and hydrogen fractions (from 25% to 75%). The effects of N-2 and CO2 addition on flame structure evolution, flame speed and overpressure histories are analyzed. The results showed that the tulip shaped flames appear in all cases regardless of whether N-2 and CO2 are added. After flame inversion, the appearance of tulip shaped flame distortion can be observed in syngas/air without N-2 and CO2 addition and meanwhile the oscillations are seen in the flame front position and speed trajectories. The flame distortion becomes less pronounced with N-2 and CO2 addition, and the oscillation amplitude of the flame front position and speed reduce accordingly. Both addition of N-2 or CO2 decrease the flame speed and the maximum overpressure. Therefore, it increases the time required for flame arriving to the discharge vent. Whereas CO2 has evidently better inhibition performance for syngas/air explosion. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.