A vacuum chamber is used as a new method to suppress gas explosion. Explosion propagation characteristics were studied in a system composed of rectangular pipes and a vacuum chamber. The volume of the vacuum chamber was adjusted by inserting PVC sheets into it. Two groups of explosion suppression experiments were conducted. In one group, the distance between the vacuum chamber and the explosive source point was 3 m and in the other group, this distance was 4 m. The results demonstrated that the effect of explosion suppression of the vacuum chamber is related to the vacuum chamber’s critical volume. When the volume of the vacuum chamber was greater than the critical volume, the chamber exhibited a good explosion suppression effect. When the volume of the vacuum chamber was less than the critical volume, it could not suppress the explosion, and the explosive pressure and flame were stronger than those measured in the absence of the vacuum chamber. On the basis of the experimental results, we further analyzed the suppression mechanism of the vacuum chamber and concluded that stretching of the explosion flame front as well as alteration of the composition of the explosive gas led to the explosive flame being extinguished.