Abstract: The XRD and TGA were used to study the ash slagging and mineral conversion of Zhundong coal(ZDC) by adding different amounts of kaolin. The results show that the original minerals in Zhundong coal mainly include calcite, anhydrite and quartz, and merwinite and dicalciumsilicate are produced at high temperature. With the increase in the blending ratios of kaolin, the ash fusion temperature decreases at first, but increases later. After adding 3% kaolin into ZDC, gehlenite, fayalite, and merwinite are the main minerals produced at high temperature, which resulting in a low tempereture eutectic. When the blending ratio is above 6%, anorthite becomes the main mineral that have a high melting point, causing a great increase of ash fusion temperature to above 1 380 ℃. The slagging index calculation shows that the kaolin can relieve the slagging degree of ZDC obviously when the blending ratio is above 6%.