Abstract: A calculation model for ore bin stability which in the southwest top slope of Yanqianshan iron mine was built during the transfer from deep open-casting to underground mining and based on the effect of rock fault.The FLAC software was used to study the ore bin stability and the surface subsidence around it.The plastic zone distribution and tension stress variation laws were analyzed under the conditions of -320 meters and -500 meters mining levels and with the subsidence as the standard to evaluate the ore bin stability.Numerical results showed that the ore bin stability decreased as the digging depth increased.When the digging came up to-320 meters，the ore bin surface subsidence within 3 mm/m and the plastic zone mainly appeared at the foot of slope with small range，indicating that ore bin and slope stable.When the digging came up to -500 meters，the plastic and tension stress zone nearly appeared all around the slope，and the influence of rock fault was significant.Overall landside slope possibility small，but slope body internal stress was redistributed，resulting in subsidence increased and ore bin instable.

Key words: Transfer from open-casting to underground mining, Numerical simulation, Slope, Ore bin stability