In order to explore the characteristics of pore and fractures at different scales and their influence on permeability, nitrogen adsorption, mercury injection and CT experiments were carried out on 14 large coal bases in China, and conducted seepage experiments on the coal samples after CT scanning. The results showed that the micropores and transition pores in each coal sample are mostly closed pores with poor connectivity, which is not conducive to the seepage of coal. The pore and fractures volume of r=10nm and r=100μm accounts for a large proportion, which contributes most of the porosity of coal. The large-scale parallel plate pores in S2 and S3 provide sufficient space for seepage. By dividing dominant pore size segments characterized by three experiments, a method for comprehensively characterizing porosity and fractal dimension is proposed. The porosity range of each coal sample is 1.62-11.60%, and the fractal dimension range is 2.29-2.78. The permeability of coal samples is between 0.0002-0.6525×10-15m2, mainly in medium and low permeability. The relationship between the porosity components of r<50nm, 50nm8.5μm and permeability is y=0.2741x-0.0781, y=0.0674x+0.0237 and y=0.0039x2.5986, respectively. The correlation between the porosity component of r>8.5μm and permeability is the strongest. Compared with nitrogen adsorption and mercury intrusion experiments, CT experiment is more suitable for analyzing the influence of pore and fractures on water seepage.