Abstract: The permeability of tar-rich coal affects the oil and gas transport during the in-situ pyrolysis. In this study, the permeability of tar-rich coal during the in-situ pyrolysis was measured via an experimental system in which the in-situ conditions can be simulated. The pore-fracture structure of tar-rich coal under various in-situ pyrolysis conditions was reconstructed by the μCT. Meanwhile, the pore-fracture network model of tar-rich coal was established by the digital core-reconstruction method. The pore-fracture structure characteristic parameters were finally obtained. Furthermore, the influence mechanism of pore-fracture structure on permeability of tar-rich coal was investigated. The in-situ dehydration, degassing, and pyrolysis cracking of tar-rich coal led to the change in the pore-fracture structure in the temperature range of 25-300 °C. The in-situ thermal decomposition of the organic matter from tar-rich coal led to the change in the pore-fracture structure in the temperature range of 300-500 °C. The permeability of tar-rich coal was positively correlated with the porosity and the maximum main fracture size, and negatively correlated with the pore-throat ratio and the tortuosity during the in-situ pyrolysis. The permeability of tar-rich coal was 5.04 mD at 25 °C and monotonically increased to 95.16 mD at 500 °C under C4.8&A4.0 MPa (representing a confining stress of 4.8 MPa and an axial stress of 4.0 MPa). By contrast, the permeability of tar-rich coal was decreased from 42.64 mD to 26.64 mD at 300-500 °C under C7.7&A6.4 MPa. The in-situ pyrolysis reaction occurred at 300-500 °C, which expanded the pore-fracture structure and reduced the strength of the coal. The compressive deformation of the coal body resulted in the closure of the pore-fracture when the strength of tar-rich coal is less than the in-situ stress, reducing the permeability. This study not only has significant theoretical value in revealing the permeability mechanism during the in-situ pyrolysis of tar-rich coal but also contributes to improving the tar recovery in applications.