Abstract: Low spiral drill rod is a new type of drill rod，which invented to solve the drilling problems of soft and outburst seam. In order to fully play the advantage when low spiral rod applied to soft coal seam drilling，the paper analysis effect on the slag removal conditions due to low spiral rod in different spiral convex edges width and pitch change according to the practical applications and establish corresponding numerical model of the slag removal. According to the dynamic parameters of the matching drilling rig in engineering application，the strength of low spiral rod has been analyzed. The result of study shows that it is optimum to slag removal result，and the minimum safety factor of drill rod strength for 1.87 with the convex edges width l=14 mm，pitch s=80 mm. It is reasonable to optimization parameter design of machining low spiral drill rod. Depth and efficiency increase significantly showing when drilling industrial experiment carried out.

Key words: low spiral drill rod, soft and outburst seam, spiral convex edges, safety factor, numerical analysis