Abstract: Aiming at the dust problems of the dry drilling in the underground mine, coal seam drilling dust-proofing apparatus was proposed to solve this problem. A systemic and deep research was conducted on the key driving element (compressed air ejector). When the number of nozzles and nozzle structure size was fixed, it analyzed the relationship between several main operating parameters of pressure-gas ejecting dust collector.Under the condition of maintaining all other structure parameters constant, the influence of changed nozzle-to-throat distance on inlet negative pressure, ejecting air volume and noise was observed respectively. The experimental results showed that the performance parameters of ejector were optimized when the nozzle outlet section and mixing chamber inlet section were coincident.