Abstract: In this paper, we established cutting discharging model of horizontal spiral rod based on the working principle of the screw conveyor with the actual situation of coal seam drilling. The formula for structural parameters of spiral rod and the amount of discharged cuttings was deduced. Meanwhile, the effect of the outer diameter, the size of rod and the pitch on the amount of discharged cuttings was analyzed. The results show that under the same rotation speed, the outer diameter, the pitch and the size of rod make great influence on the discharged cuttings amount, which can reach maximum amount when the size of pitch and rod is suitable.