Abstract: To investigate the regulatory mechanism of particle size on the microstructure and seepage characteristics of tectonically deformed coal, and further provide theoretical support for gas disaster prevention and control as well as high-efficiency coal mining in tectonically deformed coal-bearing areas, this study took the tectonically deformed coal and primary coal from Erdaogou Coal Mine in Aiweiergou Mining Area of Xinjiang as the research objects. Scanning electron microscope (SEM) was employed to observe the micro-pore characteristics of coal samples classified into five particle size ranges: 425, 850) μm, 250, 425) μm, 180, 250) μm, 150, 180) μm and 125, 150) μm. Combined with image binarization processing and box-counting fractal method, the fractal characteristics of the micro-pore structure of tectonically deformed coal with different particle sizes were quantitatively characterized. Based on fractal theory, a coal mass seepage model was established to systematically reveal the intrinsic influence mechanism of particle size effect on the seepage characteristics of tectonically deformed coal. The results indicate that: the pores of primary coal are densely distributed with poor connectivity, while the pore types of tectonically deformed coal are dominated by fragment pores, mineral-filled pores and breccia pores, presenting diverse and complex morphologies. With the decrease in particle size of tectonically deformed coal, the complexity and heterogeneity of its micro-pore characteristics are continuously enhanced. The calculation results of fractal dimension show that the fractal dimension of tectonically deformed coal increases gradually with the reduction of particle size, which directly reflects the improvement of the complexity of micro-pore characteristics. The calculation results of the fractal seepage model reveal that the permeability of tectonically deformed coal is significantly correlated with microstructural parameters such as fractal dimension and pore diameter. Specifically, a larger fractal dimension corresponds to a higher proportion of small pores during the seepage process, which consequently leads to a significant increase in the seepage resistance of coal mass.