Abstract: Based on the mineral composition, combustible content and reactivity, the comparison between the coarse slag and fine slag from the entrainedflow coal gasification was analyzed by means of TGA, XRD and combustible content measurement. The results show that the mineral composition in coarse slag is affected obviously by the gasification temperature while little in fine slag; comparing with the coarse slag, the fine slag not only has less combustible content due to its shorter residence time, but also has a lower reactivity and a larger reaction order. Furthermore, The combustible content in the fine slag increases with its particle sizes increasing while decreases in the coarse slag.