Abstract: The different influence degrees of anti-blast of wall rock reinforced by two kinds of rock bolts which have the different length around two underground openings are studied by the method of model experiments under the effect of explosive stress waves produced by focus charging. The distinctions produced by the different length of the rock bolts of stress in wall rock，surface strain of two underground openings，the roof-to-floor relative displacements of two underground openings，accelerations of roof, floor, ribs and macroscopical damage forms are compared and analyzed. The results indicate that when the wall rock of underground openings is reinforced by the longer rock bolts, the reinforcement range can be enlarged and the stressed state of wall rock of vault can also be modified, the distortion of the wall rock is restricted efficiently and the stability of underground cavern is maintained in good condition. When the rock bolts’ intervals reach a given size, the damage cracks are produced and extended outside the reinforced zone The experiment’s results provide the references of the reinforcement methods of wall rock of protection projects and tunnels.