Abstract: The classification of overburden strata is a basis of predicting the height of water conducted zone with empirical analogy.This paper applies the m phase classification to the fuzzy processing of the coal seam roof,searches for the subordinate function between the rock-native’s “softness”and “hardness”,builds the fuzzy relation matrix,makes a synthetical judgement of the roof,and uses the results to determine the coefficient value of the empirical formula which is used to calculate the height of water conducted zone.By this method,the man-made factors can be eliminated in great extent,and the height can be predicted reasonably.