Abstract: In order to select the optimal underground mining method for E'kou Iron Mine，through analyzing the occurrence condition of out of the boundary iron minerals，the alternative scheme suiting for ore mining is recommended. On the basis of comparing the technical economic，advantages and disadvantages of the alternative，the gray math model is built and the optimal alternative program is selected by using the grey situation decision，finally choosing the pillarless caving method as the best program for the E'Kou Iron Underground Mining. Meanwhile the accessory equipment for the pillarless caving method is recommended. It supplies the scientific basis and convenience under the grey situation decision used in optimizing the mining method.

Key words: Mining method, Transition from open-pit to underground mine, Grey situation decision, Mathematical model, Pillarless caving mining method