<p>To investigate the effects of microwave heating on sandstone subjected to liquid nitrogen (LN₂) freeze–thaw, the permeability measuring instrument is used to study the evolution in the gas permeability of the sandstone samples with different water saturation. The results show that LN₂ freeze–thaw declines the gas permeability of the sandstone samples except for 44.2% water saturation. Furthermore, except for the sample with 16.5% water saturation, the sample permeability increases after microwave heating. The NMR results verify that the effects of LN₂ freeze–thaw on the wet sandstone are mainly the pore collapse and pore-water frost heave. An apparent enhancement in pore structures is observed with microwave heating compared with the individual LN₂ treatments. Microwave heating removes the pore water of the sandstone samples, decreasing their saturation. When the sandstone samples are treated by LN₂ freeze–thaw and microwave heating, the enhancement in the gas permeability mainly results from the improvement of the pore structures and the decrease of water saturation. The surface temperature of the sandstone samples increases after microwave heating. With the increasing saturation, the mean temperature of sandstone samples first increases and then decreases. The surface temperature distribution of sandstone samples with a low saturation is more uneven compared with that with a high saturation.</p>