The Present paper recommands the Po-210 technique for detecting geologic structuresof coal mines,which is a new application of nuclear technique in geosciences.With this technique,ono caac detect concealed faulted Structures, concealed deprossion pillars,mined-out areas ofold workings and seam floor with well-developed water-filled fissures in coal minos.Therefore,this technipue is a rapid and economic means for tackling geologic and waterproof problems iucoal mines.Basic principles,working method, data-Processing method,detection examples and application prospects of this technique are dealt with in this paper.