To study the effect of surfactant synergistic composite acidification on the chemical structure and wetting characteristics of coal, in this paper, the influence mechanism of the chemical structure on the wetting characteristics of coal was studied. The results showed that the surfactant Sodium Dodecyl Sulfate (SDS) intensified the substitution reaction of the benzene ring structure of coal by composite acidification. The stability order of the radicals during acidification is -CH3 > -CH2 > -CH. In terms of the welling characteristics of coal, ash and fixed carbon have a greater influence on the coal contact angle than the moisture and volatile component. The aromatic and aliphatic groups are hydrophobic structures, and the OH center dot center dot center dot OH interaction has the greatest influence on the wettability and belongs to the hydrophilic group. The research results have important guiding significance for coal seams to reduce coal dust pollution and deep impact ground pressure by applying surfactants to achieve synergistic composite acidification. (C) 2020 Elsevier B.V. All rights reserved.