Abstract: For the problem that working face mining in outcrop area is threatened by boundary aquifer and need to set waterproof coal(rock) pillar, taking 1708^-1 working face in Duolun Xiexing Mine as the example, we use field measurement and theoretical analysis to determine the boundary of immersion objects aquifer, the setting width of boundary waterproof coal(rock) pillar and the hazardous area. The results show that the setting width of waterproof coal(rock) pillar of 1708^-1 working face including from the first open-off cut 0 to 530 m, 530 to 729 m and from the second open-off cut 0 to 799 m is 55.7 m, 48.3 m and 72.2 m respectively. The hazardous areas at 1708^-1 working face are from the first open-off cut 578 to 660 m and from stopping line to north 232 m. The working face is threatened by water inrush in mining process, taking the measures of aquifer grouting reconstruction or working face moving can prevent water inrush accidents.