Abstract: In the management process of mining geological environment, it is found that some mining enterprises had obvious over-exploration activities, which were usually concealed later by backfilling mining pits with mixed soil and rocks. In order to investigate the illegal liability, the administration needs to scope the actual mining area and excessive amount of over mining. Since most part of the mine pit is covered by backfilled soil and rocks, it cannot be directly measured, needing engineering exploration to reveal the interface between backfilled soil and rocks and bedrock. Studies show that the high-density resistivity and ground penetrating radar adopted as geophysical means in the preliminary exploration on the backfilled limestone pit can infer the interface between the backfilled body and the bottom bedrock, and the pit boundary in the shallow coverage area, which can provide guidance for the layout and depth design of drilling hole. The comprehensive analysis of geophysical prospecting and drilling results can determine the interface between the backfilled and the bedrock, with the comparison to licensed mining scope calculating the over-mining amount. Drilling work verify that the geophysical inference results are relatively accurate, and the collaboration of the two approaches can significantly improve work efficiency and reduce exploration costs.