Abstract: It can provide scientific basis for improving blasting scheme by understanding fan-hole blasting-induced rock fracture production mechanism.It is available to simulate blasting-induced rock fracture by using the parameters of Chenchao Iron Mine,AUTODYN software and Johnson-Holmquist(JH)model.It can record the max burst pressure by adding gauge points at bottom,middle and orifice of boreholes.The simulation result shows that denser the boreholes are,the higher pressure is and the more fracture is.The result also shows that delay detonators could dynamic increase max burst pressure of bottom rock,and the effect of delay detonators become less evident when the borehole spacing getting small,because the max burst pressure is mainly effect by the blasting stress wave of the borehole nearby.