Abstract: During the process of microwave irradiation on lignite,only the moisture and micro-components in lignite have strong capability to absorb microwave energy. If the absorber with strong microwave absorption ability is added to lignite samples during that process,the microwave upgrading process of lignite can be strengthened. Taking lignite semi-coke and activated carbon as microwave absorber,using microwave drying equipment,the experimental study of Xilin lignite on microwave drying and dehydration is carried out,and the effects of microwave absorber on lignite mois- ture dehydration in microwave field are analyzed. The enhancement mechanism of the physicochemical properties of upgrading lignite with microwave absorber is explored. The results show that the process of microwave dehydration and upgrading with microwave absorber still follows three stages ( preheating stage,rising-rate drying stage,constant-rate drying stage). During the whole drying process,the quality of microwave upgrading lignite is obviously improved,the number of oxygen containing functional groups is reduced,and the condition of spontaneous combustion is suppressed. Compared with lignite samples without microwave absorbent,the moisture of upgrading lignite with microwave absorb- ent decreases 1. 6% ,the dehydration rate increases by 9. 46% ,the dehydration rate of water loss increases 0. 013% /s;carbon content increases 2% ,the oxygen content decreases 0. 8% ;the dry-ash-free low heat and the dry-ash-free high heat increase 1 059. 318 kJ / kg and 1 059. 99 kJ / kg respectively;and the ignition can improve the maximum temperature of 23 ℃ .