Explosive specific charge is the key to the high level of casting blast. In order to study how the explosive specific charge affects the high bench cast blasting, theoretical analysis and experimental study were used in the Hei Dai-gou open pit cast blasting. Experimental study shows that: under the same engineering geological conditions and blasting parameters, the throw distance increases as the average explosives specific charge increases, and this trend slows down gradually. Settlement muck-pile height increases as explosives specific charge increases, and then gently muck-pile shape tends to be more conducive to the work platform dragline flat-field and inverted reactor efficiency. When q> 0.65 kg/m3, the cast percentage can reach more than 30%, as 0.67 kg/m3 <q <0.70 kg/m3, the cast percentage increases with a significant effect as the explosives specific charge increases; when q> 0.74 kg/m3, the increasing rate of the cast percentage with the increase of explosive specific charge decreases.