Abstract: There are some problems in Xiaowanggou Iron Mine，such as small-scale upper ore-body，narrow working space from open pit to underground mining，and deficient stopes in the first mining section，and hard to reach the expected productivity etc.In view of these problems，and on the basis of analyzing the caving possibility of ore rocks and the occurence conditions of orebody，a new scheme of three dividions based on the continuous caving of rocks was proposed.And then，according to the ranges of roof surrouding rock caving and rock movement，the safety of mining were analyzed.On the premise of keeping safety in mining，this scheme makes the productivity of underground mining in Xiaowanggou Iron Mine increase from 1 million t/a in original to 2.8 million t/a.Finally，the production practice showed that the multi-division mining technology based on the characteristics of roof surrounding rock caving expanded the work space as the simultaneous mining of open pit and underground.It not only greatly improves the productivity from open pit to underground in Xiaowanggou Iron Mine，but also achieves the exploration target with safety and efficiency.Meanwhile，it provides an effective way for high efficient exploitation of similar iron mines.

Key words: Transition from open-pit to underground, Caving, Sectional mining, Pillarless sublevel caving method