Abstract: Based on the cracking theoretical of coal blasting and combined with the engineering practice, ANSYS/LS-DYNA finite element model is established.The influence of the change of the thickness of the soft stratification on the cracking of coal is mainly discussed.The results show that soft stratification changes the way and law of crack propagation in coal body, which leads to the increase of crack in upper hard coal seam and the decrease of crack number, expansion length and distribution concentration in lower hard coal seam.The variation of soft stratification thickness only affects the fracture distribution, fracture concentration and fracture connectivity area of hard coal seam, and has little effect on the upper hard coal body.The relation curve between the thickness of soft stratification and the peak pressure is fitted.Combined with the crack theory, the crack initiation region of stratification layer coal body can be estimated, providing a reference for evaluating the crack initiation effect of soft stratification coal body and effective gas control.