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A microwave (MW) treatment method was applied to Chinese fir wood to improve its liquid permeability. It was found that the optimum parameters for the MW treatment of Chinese fir to achieve an improved permeability without significantly affecting its mechanical properties were as follows: a MW intensity of 20 kW, moisture content (MC) ranging from 40% to 60%, and a processing time of 60 s. The microscopic structure of Chinese fir wood before and after MW treatment was examined using a scanning electron microscope (SEM), which revealed that micro-checks were formed at the intercellular layer of ray cells and longitudinal tracheids; pit membranes were destroyed; and damage to cell walls was also observed. Mercury intrusion porosimetry (MIP) test results showed that the pore diameter at pit opening range increased after MW treatment (peak value of control sample: 553.7 nm; peak value of MW-treated sample: 921.1 nm) and micropores were generated, which also contributed to the improved permeability of Chinese fir wood. Positive correlations between microstructural changes and liquid permeability were found.