The relationship between the moisture content and the extraction rate of Mongolian scotch pine（Pinus sylvestris var. mongolica Litv.） wood treated by high temperature and high humidity was investigated. The changes of microstructures such as resin channels, pits and thin-walled tissues were observed through a bio-optical microscope and a scanning electron microscope. The study found that the drying time with the high-temperature and high-humidity treatment was shortened from 33 hours to 18 hours; the average extracting speed was increased from 0.057%/h to 0.151%/h; and the gradient of extractive content along their thickness after drying was reduced from 0.84% to 0.31%. Compared with conventional drying, the wood resin channel was partially destroyed after high-temperature and high-humidity treatment, and the cell wall, pore plug and pore membrane were cracked. These structural changes are conducive to moisture and resin discharging.