Abstract: To explore the evolution characteristics of the pore structure of bituminous coal and the mechanism of methane promotion under the combined action of static magnetic field and microorganisms, this research, based on the conventional anaerobic culture system, added high and low intensity magnetic field treatment groups (0, 20, 40 mT), and systematically carried out laboratory methane production rate experiments, 16S rRNA high-throughput sequencing, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and low-temperature liquid nitrogen adsorption-desorption experiments (BET). The results show that: During the 20-day culture period, the methane production rate of the low magnetic field anaerobic culture group (20 mT) was the highest, reaching 4.61 μmol/(g·h), which was 2.73 times higher than that of the control group. At the genus level, the low magnetic field treatment significantly enriched the Clostridium-sensu-stricto-1 species, with an abundance increase of 15% compared to the control group, and the proportion of acetate-nutrient methane-producing archaea Methanosarecina reached 76%. Functional gene annotation indicated that the expression of fatty acid metabolism, methane metabolism and benzoic acid metabolism pathways in the low magnetic field group was significantly enhanced. Infrared spectroscopy data showed that the addition of static magnetic field increased the proportion of fatty acid functional groups —CH, —CH₂, —CH₃ in coal, increased the microbial action sites, and thus increased the rate of in-situ microbial decomposition of each organic matter in coal. The liquid nitrogen adsorption data of coal indicated that the nitrogen adsorption capacity of the low magnetic field group was 2.25 times and 1.48 times that of raw coal and the control group, respectively, and the proportion of micropore volume reached 76.68%, and the fractal dimension also significantly increased, indicating a more complex pore structure. The SEM observations of the coal samples’ surfaces in the low magnetic field group showed more obvious coal body folds, and bacteria were visible at the same magnification. Compared with other groups of coal samples, the coal sample fissures were more developed. The research results reveal the evolution patterns of microbial communities and changes in pore structure under the influence of different static magnetic field intensities in coal samples, aiming to provide a theoretical basis for the efficient extraction of coalbed methane.