Abstract: Pore structure of coal rock has significant effect on the adsorption, diffusion and even seepage behavior of CBM. The fractal theory provides an effective method for the study of the pore structure, while there has not yet been a unified understanding of how to characterize the fractal features of pore structure of coal rock. Based on the fractal definition, we propose a new characterizing method for the fractal characteristics of coal pore structure. Then, mercury injection experiments are carried out to compare the new method proposed by this paper with the fractal definition method. At last, the fractal zone and fractal dimension values have been discussed. The results show that the fractal zone and fractal dimension values calculated by the capillary pressure method proposed by this paper are nearly equal to the values calculated by fractal definition method. So, the capillary pressure method is an effective method to identify the fractal features of pore structure of coal. The fractal dimension values can reflect the heterogeneous features of coal reservoir. When the fractal dimension values grow larger, the physical properties of reservoirs become poorer and the heterogeneous features of coal reservoir become stronger.