Abstract: In order to solve the coal dust that produced in gas drainage borehole construction in coal seam,we use drill mouth sealed with coal dust secondary separation and removal techniques to capture the dust in "three soft" coal seam during the drilling operation. In the first level,we use water jet to accelerate the coal dust and gas two phase flow and adopt comprehensive technology such as inertia, wet dust removal dust to separate the large particles;the last of the dust and gas will be guided into the secondary dust removal system through the water jet and be captured by the secondary dust removal system under the action of water jet.After the field application, the average collection coefficient reached 91%.The equipment plays well during the period of drilling roles in "three soft" coal seam.