Abstract: In order to mining the safety pillar of open-pit and underground combined mining, the technology of raw pillar replace with backfill body is put forward. The mixing proportion is designed and reinforcement computation is done, then,the scheme is be finite element numerical simulated by using the GeoFBA software, so as to analysis the law of maximum principal stree and maximum shearing stree in the process of replacement is analyzed in detail.The experimental results show that, the maximum principal stress acted on backfill body after replacement decrease obviously, only 17 kPa. The shearing stress on the bottom of surface disappeared immediately after replacement, and the maximum shearing stress concentrate phenomenon eliminate when backfilled with barren rock, so, the technology of replace raw pillar with backfill body is a feasible one, there are recyclable resource 0.37 million ton，amount of metal 1.55 ton after the project carried on. 　　

Key words: Open-pit and underground combined mining, Safety pillar, Backfill body, Replacement