Abstract: In order to research the effect of CO on the gas explosion process in restricted space, we build computational model of gas explosion in restricted space, and adopt the detailed reaction mechanisms (including 53 species, 325 reactions). The results show that CO, as the intermediate product of gas explosion, participates in CH₄ oxidation chain reaction while CO gas is filled in the mixture gases of CH₄ and air. The gas explosion time could be delayed, on the other hand, the concentration of CO₂ is increased and that of CO, NO, NO₂ is decreased during the mixture gases after explosion. With the increase of CO in gas mixture, the change of temperature and pressure during the gas explosion is firstly increased than reduced.