In view of the complex geological structure of Dawan coal mining area, advancing open branch hole distribution was adopted to detect the location of coal seam roof and floor for accurate determination of the coal seam and provide the basis for gas drainage, tunneling and mining and preparation for the follow-up work. Dawan coal mine is been defined as gas mine in the past years’ gas identification, while by ordinary drilling process in gas hole construction, large drilling workload with unqualified hole depth, difficult drilling trajectory accurate control and low gas concentration extraction rate will often be encountered. Long distance drilling in the proven coal seam can be constructed with bedding directional hole construction method to realize long-distance gas extraction in the complicated coal seam. The field test shows that by the advancing open branch hole technology, the accurate probe of complex coal seam top in the geological structure can be completed, it is found that the coal section is 75% of drilling length in a borehole. By optimizing drilling design and high precision control of borehole trajectory, the bedding directional hole coverage is greatly increased in the complex coal seam, coal section is up to 63.7% in another borehole, the gas extraction efficiency is also improved, which provides a basis for gas extracting, tunneling and mining.