Abstract: In order to obtain the influence of the change of void diameter on the behavior of blasting crack propagation, a dynamic caustic experiment method was used to study the crack propagation path,the propagation velocity and the dynamic stress intensity factor at crack tip under different pore diameters. The results indicate that with the decrease of the relative distance of the three primary cracks in the specimen,the interaction of the crack stress field is gradually enhanced,and the crack propagation velocity increases and reaches the peak value;with the increase of pore diameter, the crack propagation velocity and stress intensity factor oscillation effect are weakened in the later period of crack propagation,which is favorable for the motion cracks to expand toward the cavity;in a certain range,the larger the hole diameter is,the more obvious the guiding effect of the empty holes is on the blasting cracks;with the increase of the empty hole diameter,the trend of dynamic stress intensity factor of crack tip weakens before the three blasting cracks pass through each other.