An experimental apparatus is set up to study the methane and air mixture explosion under the effect of vacuum chamber coupled with CO2. A series of experiments have been performed to analyze the effect of CO2/vacuum chamber on explosion strength and explosion suppression. The results show that: 1) When the vacuum degree is specified at 0.05 MPa, with the increase of CO2 concentration, the explosion suppression performance of the vacuum chamber increases gradually. Under the effect of the vacuum chamber, the higher the vacuum degree is, the more significant the suppression effect is. 2) Under the effect of the vacuum chamber/CO2, the optimum suppression effect is at lower vacuum degree coupled with CO2. 3) The optimum suppression effect of vacuum chamber/CO2 is with low vacuum degree, which is better than the vacuum chamber in high degree without CO2. Therefore, coupling CO2 to vacuum chamber can improve the suppression performance of the vacuum chamber and lower the cost for maintaining a high vacuum degree. The investigation results can be used as a reference for the further research of vacuum chamber. (C) 2018 Elsevier B.V. All rights reserved.