Hydrogen is one of the alternative energy sources in the 21st century. However, the risk of combustion and explosion during utilisation poses a pronounced safety challenge, making the inhibition mechanisms of hydrogen-air premixed gas explosions a research focus. In this investigation, a 20-L explosion vessel was employed to explore the explosion characteristics of hydrogen under various atmospheres. CHEKIN-PRO software was used to study the suppression mechanism of CO2 or N2 on hydrogen-air premixed gas explosion. Firstly, the lower explosion limit of hydrogen-air premixed gas was 6 vol.%, which was slightly different from the theoretical calculation value. Then under the condition of hydrogen volume fraction of 30 vol.% and an ignition delay time of 60 ms, the explosion power was the largest. As N2 or CO2 was injected into the hydrogen-air mixture, the maximum explosion pressure decreased by 22.36% and 36.39%, demonstrating that the explosion suppression efficacy of CO2 is better than that of N2. Radical generation and sensitivity analyses revealed that N2 primarily inhibits explosions through physical dilution and disruption of reaction conditions, while CO2 exerts a combined effect of dilution, chemical inhibition, and thermodynamic cooling. In addition, key free radicals (∙H and ∙OH radicals) are consumed by N2 and CO2 in the explosion radicals R38 and R84. Furthermore, CO2 exhibits a lower temperature sensitivity coefficient and thus less temperature dependence. Inert gases also alleviate O2 concentration, lowering the probability of effective H2‐O2 collisions. These findings provide valuable insights for ensuring hydrogen energy safety in practical applications.