Abstract: Abstract: Most domestic open-pit coal mine has had a long history of underground mining, so left a large number of untreated mined-out area within the scope of open-pit coal mine, which makes up the serious threat to the production safety of the open-pit mine. The existence of them has brought serious safety hazard to the normal production of open-pit mines. Taking goaf group of mined areas in east-open pit coal mine of PingShuo for the research object in this paper, establishing coal geology model and goaf group model by using geophysical methods and 3DMine mining software, according to the actual situation of stripping stages, the author will do research by stages and layers on stability of overlying rock mass in goaf. The research results are significant for guiding the actual production of open-pit mine , protecting the safety of life and property of operators , machinery and equipment.