Abstract: With the application of high-step steep slope mining technology in open-pit mines in China，pre-splitting blasting control technology has become an important means to protect slopes and control secondary disasters caused by blasting vibration. In order to accurately calculate the key process parameters of pre-splitting blasting (line charge density) and the width of pre-splitting joints under different line charge densities in the mine's adjacent area， the Wushan Copper-molybdenum Mine was taken as an example， combined with rock mass failure judgment and the explosive pressure law of explosives， the formula for calculating the charge density of the pre-split blasting line was theoretically deduced，and the theoretical formula for the charge density of the pre-split blasting line when the pre-split hole was cracked and the pre-crack penetrates was obtained， combined with the typical mine lithology-biotite granite，the physical and mechanical test parameters were calculated.It is showed that the linear charge density of typical rock cracking and pre-fracture penetration in the mine were 0.196 kg/m and 0.528 kg/m， respectively.Through numerical simulation and regression analysis， the relationship between the line charge density and the width of the pre-splitting blasting seam was analyzed， and four schemes of line charge density 0.50， 0.54， 0.57， and 0.6 kg/m were selected. Statistics on the failure of grid elements in the whole process of forming through cracks showed that when the linear charge density was 0.5~0.6 kg/m， the pre-fracture width and the linear charge density could be described by the following functional relationship: y=- 172x2+213x-60 （R2=0.98）， and the width of the pre-crack increased with the increase of the line charge density. An on-site pre-splitting blasting test was carried out in the test mine， and the blasting vibration at 30 m behind the pre-crack was monitored. The results showed that the comprehensive vibration reduction rate at 30 m behind the penetrating pre-crack reached more than 31.3%； The pre-crack has the phenomenon of bonding and bonding， and the damping effect was significantly reduced. Compared with the pre-crack penetration， the vibration damping rate wasreduced by 4.3% to 5.6%； When the pre-crack is penetrated， the line charge density further increased to 0.06 kg/m，the vibration reduction rate was only increased by 1.3%.The further analysis showed that after the pre-crack was completely penetrated， continuing to increase the line charge density has no obvious significance for the improvement of the vibration reduction effect.

Key words: mine blasting, pre-split blasting, slope control, through cracks, line charge density, numerical simulation