Abstract: The Water seepage and hydrostatic pressure have major impact on the slope around the reservoir and the stability of the mined area. To understand the effects of reservoir permeability after impounding water on slope stabilitjy and stability of hydraulic mining of the deep, and guarantee the security of underlying stope, the numerical model based on the actual terrain conditions was established. The mechanical properties and displacement changes of deep mining on the surrounding rock mass slope and gob roof before and after water storage was simulated around the entire reservoir surface. Then the stability of reservoir storage on the slope and mined-out area was analysis. The results show that the displacement of surrounding rock on the goaf roof is not obvious after impoundment, and the local area produces stress concentration but does not exceed the maximum load of rock which is in the factor of safety limit; the stability of reservoir slope is less affected by the water seepage and the reservoirs slope is more stable than the other place.