Abstract: In order to control the coal dust disaster in the fully mechanized top coal caving mining face in thick soft roof-floor coal seam, the forces between dust particles -and the water injection dust prevention mechanism were theoretically studied. According to the geological conditions of the 1st coal mine of Pingyu, the deep borehole water injection was used to reduce the high coal dust. The results showed that the liquid bridge force was the key factor to reduce the high coal dust. After the deep borehole water injection, the moisture content of二1- 13110 working face (3% before the water injection) was increased to 5% ~ 7% . In addition, the coal dust content of the different sites of the working face was decreased by more than 50%. The water injection has obvious anti-dust effect, which provides a reference for the treatment of coal dust disaster in soft roof-floor coal seams.