Abstract: In this paper, the natural classification of the cover rock grain size, the influence of the ore blasting effectiveness on the ore loss and dilution in the sublevel caving mining without the bottom pillars are presented. Through the theorical research, pilot test, commercial test and application, it has been proved that by using the bore hole-bottom cavity blasting can obtain an uniform ore grain size, good fluidity and decreased ore loss and dilution.By testing with the cement grout models, the space form of caved down ore has been gotten out.This provides a guide effect to optimize the ore-drawing parameters and to research the ore-drawing theory.