Abstract: In view of the large and high gas coal mine, the problem of drilling and excavation is becoming more and more outstanding, this paper introduces the components and working principle of directional drilling machine. The equipment includes all hydraulic power head type crawler drill rig, measuring probe, cable pipe, orifice monitor, and realizes directional drilling and control of drillings through using orifice monitor of computer automatic control system to carry on quantitative calculation of screw drill anti torsion angle. Finally, the field test was carried out, and the results showed that the main hole depth exceeds 500 m, the success rate was 80%, all parameters reaches the expected target, drilling rig can meet the needs of the actual production of coal mine.