Abstract: To improve the dust reduction efficiency of coal seam water injection, two kinds of non-ionic and two kinds of anionic surfactants were selected to study the surface tension and wetting characteristics of monomer and composite surfactant solutions. The synergistic wetting effect of composite surfactant solution on hydrophobic coal is compared and analyzed, the mechanism of synergistic wetting is discussed, and the field test of coal seam water injection is carried out. The wettability experiment of monomer surfactant shows that the wettability of the four surfactants is still gradually enhanced after exceeding the critical micelle（ＣＭＣ） concentration. The experimental results of synergistic wettability of composite surfactant show that there is a significant synergistic effect between non-ionic surfactant TX-100 and anionic surfactant DSS, and that the synergistic effect gradually increases with the increase of surfactant mass concentration. When the total mass concentration was 1%, the synergistic rate was 60.06% and 132.03%, respectively, compared with TX-100 and DSS monomer solution. The mechanism of synergistic wetting was analyzed based on the principle of interfacial chemistry. It was found that the key reason for the synergistic wetting effect of hydrophobic coal dust was the significant increase of the dissociation rate of surfactant micelles in high concentration composite surfactant solution. The coal seam water injection test was carried out on the fully mechanized excavation face. After adding 1% TX-100: DSS composite surfactant solution for water injection, the dust reduction rate reached 71.04%, which was 43.45% higher than that of adding 0.05% TX-100 solution, indicating that the high concentration composite surfactant has a significant synergistic wetting effect on hydrophobic coal.