Abstract: Based on current status analysis of underground gas drilling technology of coal mine at home and abroad, the paper introduces the construction equipment and technology of a nearly horizontal directional long drilling for a coal seam. And the effects on gas drainage by the long seam directional drilling and the ordinary drilling for the coal seam are compared with a case, obtaining that the long directional drilling has some potential advantages. Meanwhile, the problems which affect the drilling efficiency and depth in construction of long nearly-horizontal directional drilling in China's coal mines are pointed out. To solve these problems, a long directional drilling technology and the key technique of branch drilling are proposed, and its effectiveness is finally verified through the field tests.

Key words: Coal seam, Gas, Nearly horizontal directional long drilling, Holes branch open