Abstract: Based on the conditions of open pit and underground mining of Guilaizhuang gold ore, the stability of different thickness boundary pillars was assessed with considering the effect of static load and dynamic load, respectively, by using software of FLAC^3D. Under dynamic load, blasting construction load was simulated with usual triangular wave, the vibration velocity and the stress distribution laws of different thickness were then achieved. According to the statistical relationship and the tensile strength standards of rock, the threshold vibration velocity for the boundary pillars with different thickness was analyzed. The results showed that the relationship between the vertical vibration velocity and the maximum tensile stress is linear. The maximum vibration velocity of a particle can be used as the safety criterion. When the ore room span is 8, 10 and 12 m, under the dynamic loads, the minimum safety thickness is 8, 14 and 18 m, respectively.