Abstract: To study the influence of pressure and aqueous solution viscosity on coal seam seepage characteristics, numerical simulation method was adopt to study the distribution of pore pressure in coal seam considering different water injection pressure. The effect of adding permeation-promoter on the seepage effect was examined as well. The results indicated that 8 MPa medium-pressure water injection process conforms to the general production requirements at required condition; the pressure has an obvious effect on water seepage drive in coal seam; the effect of gravity can be ignored in the coal seam; the adding of permeation-promoter can obviously improve the effective wetting range. When the viscosity coefficient of water solution is 50%, the effective wetting radius of the coal seam is increased by 49.76% compared with that of the water, which decreases the task of drilling.