Abstract: Taking No. 8 coal seam in Wulunshan Coal Mine as the research object, the coal samples were soaked with water, acetic acid and different surfactantsin acetic acid, then the pore characteristics of each sample coal were analyzed by mercury injection method, and the pore fractal was calculated based on Menger sponge model and Sierpinski gasket model. The results show that the pore distribution of all samples is "M" type; raw coal and mercury curve of coal samples treated with water and acetic acid have a large hysteresis loop, and the hysteresis loops of the mercury curve decrease when different surfactants are added to acetic acid; among the fractal dimensions calculated by Menger sponge model, the seepage and adsorption pore fractal dimensions of coal samples with NBSP are 2.76 and 2.92, and the fractal dimensions of other samples are greater than 3; the fractal dimensions calculated by the Sierpinski gasket model, and the fractal dimensions of coal samples treated with water increases, while the others decrease.