Abstract: According to the characteristics that the composite roof is easy to appear failure and instability due to tensile damage, the decision model for separation layer of composite roof is given based on the damage analysis of surrounding rock. The Weibull statistical function and Mises yield criterion are used to analyze the damage parameters of the surrounding rock. Combined with the deflection calculation formula of composite roof rock, the separation layer position of composite roof is determined from the bottom up and the separation layer value is calculated. The results show that the modified model is successfully applied to the separation layer determination of composite roof, and the actual measured error is only 3%.