Abstract: It is one of the key technical problems for mines that transit from open-pit to underground mining to confirm transitional scheme from open-pit to underground mining rationally.Taking Miaogou iron mine as the research object，based on the systematically analysis of the stage of the end of open-pit mining and the occurrence of ore body which is outside the boundary，the infrastructure time and annual production capacity are firstly determined after designing the mining scheme of different districts.Then，on the basis of the exploitation status quo and plan，combing with the formation plan of covering layer and mining schemes of hanging wall ore body，four transition schemes were put forward by analyzing the time-space relationship of transitional period.Finally，in order to achieve a smooth transition，such indexes as investment，resource utilization coefficient，smooth capacity coefficient and mining safety coefficient are regarded as the evaluation index of scheme optimization combined with existing norms and standards.Fuzzy comprehensive evaluation theory is used to optimize the feasible schemes，and the transitional scheme determined finally is that the northern hanging wall ore body will be mined by caving method，and the western hanging wall ore body will be recovered by combination of footrill and chute，and then backfill to form the covering layer.

Key words: Iron mine, Transition from open pit to underground, Transitional scheme, Optimization, Evaluation index