When forming the lower part of the working zone of the open pit - opening and preparation of new horizons - insufficient attention is paid to the shape of the excavated space of the lower horizon, which often cannot provide the most rational parameters of the blasted block, and therefore the maximum length of the mining front, which should compensate for the deficit arising from the mining front on the upper horizons. The present work provides the formation of the shape and parameters of the preparatory excavation, its position relative to the ore deposit and ensuring the maximum length of the mining front, taking into account the rational use of drilling and blasting.