An experimental study of hydrogen/air premixed flame propagation in a closed rectangular channel with the inhibitions (N-2 or CO2) was conducted to investigate the inhibiting effect of N-2 and CO2 on the flame properties during its propagation. Both Schlieren system and the pressure sensor were used to capture the evolution of flame shape and pressure changes in the channel. It was found that both N-2 and CO2 have considerable inhibiting effect on hydrogen/air premixed flames. Compared with N-2, CO2 has more prominent inhibition, which has been interpreted from thermal and kinetic standpoints. In all the flames, the classic tulip shape was observed. With different inhibitor concentration, the flame demonstrated three types of deformation after the classic tulip inversion. A simple theoretical analysis has also been conducted to indicate that the pressure wave generated upon the first flame-wall contact can affect the flame deformation depending on its meeting moment with the flame front. Most importantly, the meeting moment is always behind the start of tulip inversion, which suggests the non-dominant role of pressure wave on this featured phenomenon. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.