Abstract: During coal exploration, vertical projection and vertical equidistant maps are composed for coal seams with inclination larger than 60°. However, when folds are very developed and vertical even reversed, and have highly changed dip and strike in a working area, those maps can not sufficiently reflect the form of coal seams, which causes difficulties for reserve estimation. To resolute the problems, we can compose vertical developed map, in wich each wing of a fold is projected into a reference plane, then pieced together according to the continuity. From a vertical developed map , we can see clearely the area of each projected seam, the extent influenced by a fold or a fault ,therefore,the degree of control by prospecting work.