Abstract: Micro-nano pore structure is one of the main occurrence spaces of gas. Exploring the evolutionary mechanism of micro-nano pore in TDC under the influence of dynamic metamorphism can help to deepen the understanding of coal and gas outburst mechanisms. The evolutionary characteristics and mechanism of micro-nano pore structure of different types of TDCs developed in 7₂ coal seam of Qi'nan Coal Mine in Suzhou were studied by CO₂ adsorption experiment, Fourier transform infrared spectroscopy (FTIR) test and molecular dynamics simulation. The results show that with the increase of tectonic deformation, the pore size of ultra-micropores (0.3 ~ 0.7 nm) shifts to the direction of small pore size, the fractal dimension of micro-nano pore volume and the fractal dimension of specific surface area increase, the heterogeneity increases, and the complexity of pore structure increases. The results of molecular structure test and molecular dynamics simulation indicate that brittle deformed coals mainly occur through stress degradation. The breaking and dissociation of hydrogen bonds, aliphatic side chains, and oxygen-containing functional groups in the coal molecular structure enhance the activity of the molecular structure, and under the action of tectonic stress, the coal macromolecular structure is initially compressed; The brittle-ductile and ductile deformed coals undergo significant stress condensation, and the aromatic structure in coal can undergo chemical changes such as rotation, folding, and recombination, forming a more tightly arranged molecular structure configuration of coal. Therefore, with the enhancement of tectonic deformation, the structure of coal macromolecules is continuously compressed and changed, and the gaps between molecular structures are divided, resulting in changes in the morphology and size of micro-nano pore structures, an increase in pore complexity, and an overall shift in pore size towards smaller pore sizes.