Abstract: In order to study the variation rule of the safe thickness of overlying strata under multi-factor coupling, the safe thickness of roof was analyzed for the proved goaf in Hequ Open-pit Mine. Numerical model of mined-out area and the surrounding rock mass is established, the change laws of different spans mined-out area under shock load factor and double superposition of goaf roof subsidence displacement are analyzed. The results showed that the mined-out area overburden safety thickness increases with the increase of the span mined-out area, and when the span of goaf reaches 60 m, the upper strata will be seriously damaged; the influence of vibration load becomes more obvious with the increase of goaf span considering vibration load. The spacing range of goaf with superimposed influence is within 40 m. Based on the theoretical analysis and numerical simulation results of safety thickness of overlying strata in goaf, the disposal plan of goaf in Hequ Open-pit Mine is given.