In this research, Mongolian scotch pine（Pinus sylvestris var. mongolica Litv.） was used as raw material to prepare microwave puffed wood. During the treatment, the maximum temperature at the center of the wood reached 183 °C. Microwave power density and initial moisture content and the interaction of these two factors showed a significant effect on the content changes of the three major components in the samples. The relative content of lignin increased compared with untreated wood, while the contents of cellulose and hemicellulose decreased less than 5%. The contents of cold water extractive, benzyl alcohol extractive, and 1% NaOH extractive of treated wood samples decreased with the escaping of water vapor during the treatment. The pH value of the puffed wood samples increased but the wood stayed acidic. The ash content remained unchanged.