Abstract: In order to study the effect of bacterial anaerobic degradation on coal pores and fractal characteristics, the development of coal pores was characterized by high-pressure mercury injection and low-temperature liquid nitrogen adsorption. Menger model and FHH model were used to analyze the fractal characteristics. The results showed that after anaerobic degradation of bacteria, the micro-pores, transitional pores and meso-pores of residual coal were reduced, and the specific surface area was reduced more significantly. But at the same time, the large pore volume was increased. Besides, the dimension was obviously reduced, the surface roughness was reduced, and the pore development tended to be simple. These results showed that after anaerobic degradation, the coalbed methane adsorption capacity of bituminous coal reduced, while the seepage capacity partly increased.