The utility model relates to an open -pit field bench blasting pore structure, including pre -splitting hole, main hole, the three group big gun holes of blast hole of exploding, pre -splitting hole and blast hole all adopt the deck charge mode, and from top to bottom the former reduces the explosive load in proper order, and the latter increases in proper order, and whole powder charges are all adopted in all the other drillings, and backfill on all equal upper portions in big gun hole. The blasting in -process, the at first detonating presplitting hole that is close to presplitting face oneside to form the presplitting face, adopt millisecond blasting between all the other big gun hole, between arranging, make explosive energy utilization ratio maxmizing. The utility model discloses a vertical hole, its construction is comparatively simple, requires not highly to the rig, the powder charge process adopts deck charge, can effectively utilize the blasting effect of each district's section to form ideal bank slope angle, reduces later stage rock overburden amount, the last earlier detonating pre -splitting hole of blasting time to form the presplitting face, adopt millisecond blasting between surplus big gun hole row, hole, with rational utilization explosive energy, reach best blasting effect.