Abstract: The gasification reactivity of raw coal, filter cake and the slag in demister from an industrial gasification plant was investigated with steam and carbon dioxide as the gasification agent. The initial structure and surface characteristic of the samples were analyzed by scanning electron microscope and adsorption apparatus. The results show that the gasification reactivity of the raw coal is better than that of the slag in demister, while the gasification reactivity of the slag is similar to or a bit better than that of filter cake, which is mainly attributed to the extraordinary difference of surface and internal structure of these three samples. As a result of different reaction mechanism with steam and CO₂, the gasification reactivity of the samples with steam is about 3 times higher than that with CO₂.