Abstract: Method of three-step-extraction was used to research the existing form of alkali metals in Zhundong Coal. Coal samples were placed in the tube furnace which was in inert atmosphere to study the migration of alkali metals varying with temperature from 400 to 1000 ℃. Finally, the release forms of alkali metals from coal ash during pyrolysis process were simulated by Factsage. The results show that sodium in Zhundong coal exists mainly in the form of water soluble sodium, while potassium is in the form of organic potassium and insoluble potassium. The content of water soluble sodium in Zhundong coal descends obviously in the process of pyrolysis and the release rate is the fastest at the temperature between 400 to 800 ℃, While the concentration of water soluble potassium is stable. Replacement reaction will take place at high temperature. The results of experiment and Fact Sage indicate that, in the pyrolysis process, alkali metals are released mainly in the form of chloride.