Abstract: Stress equilibrium state of stope overburden is destroyed by underground caving mining，which causes the surface distortion and rock layer movement，so the surface construction safety is affected.Because deep ore-body of  Dahongshan is exploited with caving，which will affect the stability of open pit.Influence of ore-body excavation on open pit was studied by FLAC3D numerical simulation method.The results showed that security pillar reserved，the southern ore-body excavation at 400 m above don't affect open pit by calculating the movement angle of 65°，so open project is still stable overall.But if security pillar is not reserved，open pit would be affected by ore-body excavation at 400 m above.The research results could offer instructive basis for safety production of open pit

Key words: Underground mining, Open pit, FLAC3D, Security