Abstract: An experimental procedure was tested for studying the sintering and fusion characteristics of fly ash from anthracite fluidized bed gasification at the temperature approaching the ash deformation temperature (DT), and the slagging characteristic was investigated. The quantitative analysis on the composition of crystalline mineral matter and the amorphous phases in the thermal treated ash was carried out using X-ray diffraction analysis (XRD). Experimental results show that the slagging tendency of fly ash is related to the transformation of minerals. AFTs of fly ash are lower than those of original coal due to higher contents of Fe, Ca, and Mg. The formation of melting matrix causes a liquid-phase sintering at 100~200℃ below the DT, which leads to a shrinkage deformation and clinkering due to the formation and transformation of feldspar that plays a 'glue’ role in sintering. A great amount of Ca and all of Fe are found in the glass phase, which improves the amorphous phase in concentration. These fluxing components in the glass phase that do not crystalize during thermal treatment can promote the densification process of sintering and the slagging or agglomeration tendencies.