“Three unders” in coal mining technology was explored in this paper, principle and connotation of "mining -selecting-filling" technology was elaborated, as well as existing key and difficult points. At the same time, its efficient operatioanal arrangement form was researched. After application of “mining -selecting-filling” technology, subsidence under the influence of mining processed field mearsurement to ensure its feasibility, which not only provided technical solutions to “three” coal mining, but theoretical reference to prevention of ground surface seetlement, dispose of gangue waste and mining of coal resources under similar occurrence conditions.