Abstract: For coal and rock properties, we make coal element strength subject to truncated normal distribution, and then introduce a variation coefficient to establish a statistical damage model applied to coal seam damage process. The results show that this model shows more reasonability in showcasing the evolution characteristics of damage. Parameters μ and δ, respectively, respond to the uniformity distribution of coal seam macro-scale failure strength and element strength; macroscpic strength is positively correlated with parameter μ, while it is negatively correlated with parameter δ. By further analysis of dimensionless macro-scale strength, we find that it’s related to variation coefficient only.