Abstract: The lignite from eastern Inner Mongolia was treated under six different powers and different drying times in the microwave field. Under different microwave processing conditions， chemical titration method and low temperature liquid nitrogen adsorption method were used to examine the amounts of oxygen-containing functional groups and pore structure, respectively. And at the same time，pore size distribution，specific surface area and pore volume of raw coal and coal samples under different microwave treatment conditions were characterized. It was found that microwave power 600 ~ 800W， processing time 4 ~ 8min can enhance the stability of lignite upgrading.