Abstract: As an innovative water-free fracturing technology, liquid-nitrogen fracturing is capable of effectively improving coal-seam permeability. Nevertheless, fractures induced by this technology are readily closed under in-situ stress, which restricts the permeability-enhancing efficiency. Changes in pore structure and stress-sensitivity of coal subjected to vertical in-situ stress after liquid-nitrogen fracturing therefore need to be investigated, so as to optimize process parameters of liquid-nitrogen fracturing and formulate reasonable schemes for gas-drainage spacing and proppant arrangement. Typical low-rank, medium-rank and high-rank coals are selected as research subjects. Combined with liquid-nitrogen freeze-thaw cycles, mechanical tests and nuclear magnetic resonance (NMR) technology, variations in mechanical properties of three coal ranks under different liquid-nitrogen freeze-thaw times, as well as the pore-structure evolution of freeze-thaw-treated coal samples under stepwise axial-stress loading, are explored. Relationships of porosity stress-sensitivity with coal rank, stress and freeze-thaw times are further established. The results demonstrate that the compressive strength, elastic modulus and wave velocity of the three coal samples are reduced after liquid-nitrogen freeze-thaw cyclic treatment, and significant negative correlations are identified between these mechanical parameters and cycle times. Within a certain stress range, pores and pore throats are shrunk under axial stress. Such pore-shrinkage behavior is aggravated for freeze-thaw-treated coal samples owing to the degradation of mechanical properties, and the maximum pore-closure degree reaches 0.679%. Damage variables determined from porosity, acoustic velocity and elastic modulus of freeze-thaw-treated coal are positively correlated with freeze-thaw times. The two-parameter damage variable defined by porosity and wave velocity exhibits higher accuracy, and the damage degree follows the order of lignite > bituminous coal > anthracite. Both the stress-sensitivity coefficient and porosity compressibility decrease linearly under low-stress conditions. When the porosity compressibility is greater than zero, these two parameters are elevated with the increase of freeze-thaw times. Among the three coal ranks tested, the stress-sensitivity is ranked as lignite > bituminous coal > anthracite. It is revealed that liquid-nitrogen freeze-thaw treatment markedly exacerbates the tendency of pore closure and damage failure of coal under stress. Theoretical references are provided for the quantitative analysis of fracture closure behavior of liquid-nitrogen-fractured coal under in-situ stress and the optimization of gas-drainage parameters.