In order to solve the problem of large amount of flour dust output in the fully mechanized caving work of Yutai Mine, by comprehensive on-site investigation and analysis, the working dust concentration was monitored, and the dust reduction measures for pre-wetting coal in coal seam long hole water injection were proposed. The selection of the water injection parameters were studied. The research showed that the reasonable water injection parameters were, water injection hole depth 45 m, spacing 12 m, height 1.5 m from the floor of the roadway, water injection pressure 8 MPa, water injection time 60 h, after the water injection, the total dust concentration of the working surface was reduced by about 50%~60%, the dust concentration was reduced by about 60% ~ 70%.