Abstract: In order to quantitatively characterize the effect of carbon dioxide fracturing on the pore structure of coal, the M8 coal seam of Dayun Coal Mine was used as the research object to carry out carbon dioxide fracturing. Four groups of coal samples were tested by mercury injection and scanning electron microscope, and fractal characteristics were combined to analyze the coal samples before and after cracking. The results show that carbon dioxide fracturing has a significant effect on coal pores. Mercury injection test results show that the pore volume, average pore diameter and porosity of coal samples all increase, and the specific pore surface area will increase within the range of about 1 m close to the cracking hole, and then the cracking effect will be weakened with the propagation of the cracking impact. The fractal dimensions of the four groups of coal samples were calculated by the mercury pressing experiment and the electron microscope scanning experiment. After cracking, the fractal dimensions were all smaller than that of the raw coal. The fractal dimension of 4 groups of coal samples is 1# < 2# < 3# < YM from small to large. The results indicate that carbon dioxide cracking can promote the development of pore structure and the connectivity between pores in coal samples.