Abstract: In order to improve the drilling depth of the gas drainage borehole and the gas drainage effect in the underground mine, the mine horizontal directional d rilling technology was applied to the horizontal long borehole drilling and the multi branch borehole drilling in seam.The directional drilling technology and the borehole accomplished method under different seam conditions were systematically introduced.Then according to the in seam construction features of the directional drilling, the complicated geological conditions, the difficult control of the dilling tracing, the complicated driling accident and other technical difficulties in the horizontal directional drilling in seam were analyzed.The site construction experiences were summarized and a completed set of the common drilling tools combination, construction procedur e, drilling tracing control and technique method suitable for the directional drilling construction were formed. The successful applications of the directional drilling technol ogy to DuDerping Mine and Shuangliu Mine showed that the max depth of the drilling could be over 500 m and over 90% of the seam drilling could meet the constructio n requirements of the gas drainage borehole.