Except for rock mass quality,blasting load and in-situ stress are the two main factors for rock cracking and blasting damage zone developing.To reveal the rock cracking process during pre-split blasting,the numerical simulation model of damage zone around a single-hole and double-holes are analyzed through ANSYS/LS-DYNA.Various kinds of cases with different in-situ stress levels and states are discussed.A simplified empirical equation(1)is established to describe the correlation between peak particle vibration(PPV)and damage extent index,and the linear charging density under different in-situ stress levels is also evaluated.The result indicates that the damage zone decreases with increasing of the in-situ stress level.The damage zone mainly develops along with the direction of major principal stress,which has been verified during the excavation of abutment slot in the Baihetan Hydropower Station in China.Thus,to increase the effects of presplit blasting,linear charging density should be reasonable and the connection line of presplit blasting holes should be parallel to the major principal stress.Equation: The relationship between PPV and damage extent index:D=1-(V0-V/V0)2(1)Where D is the damage extent index,V is the peak particle vibration(PPV),V0 is the PPV on the blast-hole wall.