There are a number of parameters related with mining method optimization of transferring large scale openpit into underground mining, of which many have fuzzy features. Based on deposit and mining conditions of the Nanfen iron mine, the ideal point method and the Hamming approach degree method were used for primary selection of possible underground mining methods. The fuzzy multi-attribute decision-making method was used for final optimization of mining method to ensure adaptability and comprehensiveness of underground mining method selection. A subjectiveobjective coupling weighting method was used to determine weights of various factors influencing mining method selection, which would prove reasonableness of determining weight coefficients. Finally, the sublevel caving method with no sill-pillar was selected as the underground mining method to be used in the Nanfen iron mine. According to the comments of mining experts in a judging meeting, the selected m ethod would fill requirements of mining techniques and mining benefit.