Abstract: An important research mean for coal and gas outburst is to accurately classify of the breakage degree of the original coal, but the classic five levels cannot meet the quantitative study of coal and gas outburst at present. Through the analysis of the failure process of coal by geological tectonic stress, 3 models of the particle size and extent of the breakage were built, including the screening index K of 0.5 mm particle, the fineness modulus P, and the mass fractal dimension D. The D value that has advantages of good correlation degree, clear mathematic significance and plentiful data can be used to describe the quantitative index of the breakage degree of the coal mass. The higher of D value is, the more severe of the breakage degree of the coal mass is.