Abstract: An iron mine in Inner Mongolia is limited by the plane range of mining rights，and the minimum mining elevation of the final boundary is 1 500 m. The open-pit residual ore body and deep ore body need to be transferred to underground mining. Two mining methods，non-pillar sublevel caving min⁃ ing method and sublevel filling mining method，suitable for mining technical conditions are put forward. The mine production capacity，designed ore quantity，investment cost，sales revenue and national industri⁃ al policy are compared and analyzed. Finally，the sublevel filling mining method with less ore pressure， high ore recovery rate，small area of waste dump and tailings pond and avoiding surface collapse was select⁃ ed. The process design of the selected mining method is carried out，and the stope structure parameters and mining technology are determined.

Key words: open-pit to underground mining, fill mining method, recovery process