The suppressive effect of multi-layer wire mesh structure on the combustible gas explosion is studied. Two new important concepts, critical quenching value and critical quenching pressure difference are proposed. Both flame propagation speed and pressure difference are considered to describe the explosion suppression result. Critical quenching value is used to determine the suppression capability of the suppressive structure. The relationship among critical quenching value, critical quenching pressure difference and geometrical parameter of suppressive structure of multi-layer wire mesh is studied. And the empirical formula of the relationship is obtained. With the increase of geometrical parameter（n·M·d）, critical quenching pressure difference and critical quenching value increase, moreover,the quenching capability is improved.