Abstract: In view of the characteristics of large coal dust production, fast flow rate and high gas content in the air directional drilling of broken soft coal seam, the dust removal device of negative pressure suction and classification purification was designed for air directional drilling of broken soft coal seam, based on negative pressure suction inertia dry dust removal principle. The device was mainly composed of orifice dust collector, primary dust collector, secondary dust collector, dust bag and supporting pipeline, etc. The orifice dust collector collects the coal dust and gas from the orifice. The primary dust collector separates the medium and large particles of coal dust, and the dust bag collects medium particles of coal cinder and exhales non-gas gas in the coal dust stream. The secondary dust collector uses underground gas to extract the negative pressure and actively sucks the gaseous gas in the coal dust. The application test was carried out during the air drilling of soft broken coal seam in Qinglong Coal Mine, and the coal dust removal of nine air directional long boreholes were completed. The hole dust collector was well sealed, and there was no leakage of coal dust and gas. The dust removal rate in drilling field was more than 96%, which effectively improved the working environment of drilling site. At the same time, the dust removal process did not use water, cinder cleaning was convenient and fast, saving water resources.