Under 900 W, the effects of microwave irradiation time on the solid concentration, rheology and static stability of lignite water slurry (LWS) were investigated. The results showed that with the gradual increase of microwave irradiation time the hydrated film on lignite became thinner and it contributed to the maximum solid concentration of lignite increased from 51.63% to 55.30% (irradiated for 12 min). At the same time, the oxygen/carbon and hydrogen/carbon atomic ratios decreased, the moisture content and oxygen-containing functional groups gradually removed, and the lignite surface became smooth. The changes of these interfacial properties improved the pseudo-plasticity and reduced the yield stress of LWS. Besides, the changes in lignite surface caused larger dispersant adsorption on lignite surface and therefore enhanced the static stability of LWS. (C) 2016 Elsevier Ltd. All rights reserved.