Abstract: In recent years,the researches on gas explosion suppression and explosion-proof technology worldwide main- ly focus on explosion suppression agent,energy-absorbing material and vacuum cavity. It is pointed out in the litera- tures that the cavity has the function of explosion suppression,and the effect of explosion suppression depends on the volume of the cavity. In order to explore the influence of cavity size characteristics on the suppression performance of gas explosion propagation,rectangular steel cavities with a wall thickness of 10 mm and a volume of 0. 08 m3 and an aspect ratio of 5 / 8 and 8 / 5 were designed respectively. The cavities were installed respectively in a large pipeline sys- tem with a length of 36 meters for carrying out experimental research,and investigating the variation of gas explosion flame and shock wave overpressure after passing through the cavities. The results showed that the cavity with an aspect ratio of 5 / 8 inhibits the propagation of explosion flame and shock wave. The cavity with an aspect ratio 8 / 5 inhibits the explosion flame,but enhances the propagation of shock wave. On this basis,a numerical model was established,and the cavities with a volume of 0. 08 m3 and the aspect ratios of 1 / 10,2 / 5,5 / 8,1,8 / 5 and 5 / 2 were attached respectively to the pipeline system for carrying out numerical simulation. It is found that the inhibition effect of cavities on the propa- gation of gas explosion shock wave depends on the aspect ratio of the cavities. The smaller the aspect ratio is,the stron- ger the inhibition effect of cavities on the propagation of shock wave,and there is a critical aspect ratio. When the as- pect ratio is less than 1,the cavity inhibits the shock wave propagation. When the aspect ratio is greater than 1,the cavity enhances the shock wave propagation. When the aspect ratio is 5 / 2, the enhancement is most obvious. The mechanism of the influence of cavity aspect ratio on the propagation of gas explosion shock wave was analyzed. The greater the aspect ratio of cavity is,the more the reflected wave can be received at the outlet and the inlet,and the greater the overpressure of shock wave generated by the superimposed reflected wave at the outlet and the inlet,and vice versa. The greater the aspect ratio of the cavity is,the more premixed gas is involved in the explosion in the cavi- ty,the more intensive the explosion in the cavity is,and vice versa. Therefore,the greater the aspect ratio is,the worse the inhibition effect of cavity on the propagation of gas explosion shock wave is,and otherwise the better the inhibition effect is. When the aspect ratio is greater than the critical aspect ratio,the cavity will enhance the propagation of gas explosion shock wave.