Abstract: Typical minerals in coal can be divided into six types:clay mineral,sulfide,phosphate,carbonate,sulfate and other minerals. The evolution process of minerals in coal under the temperature increasing process has big effect on viscosity-temperature characteristics of coal ash,therefore,the minerals constitution has certain effect on application range and utilization path of coal. Through analyzing the main minerals constitution in coal and variation low of different minerals groups under the temperature increasing process,the reference of gasification raw coal selection and viscosity-temperature characteristics adjustment of gasification coal ashcould be provided.In this paper,the conversion processof main minerals in coal under high temperature and the main product of process were demonstrated. 8 kinds of minerals such as kaolinite,illite and pyrite were divided into 3 groups according to their mineral characteristics,The simulation study was carried outrespectively by utilizing the FactSage software in the temperature range of 1 000～1 600 ℃. The inert atmosphere was selected in calculation process,and the calculation was done once every 100 ℃,and every mineral was calculated as amount of 1 mol. When a new mineral appeared,or an old mineral disappeared,the minerals constitution at this temperature was calculated as well. The results show that,in the system which is composed of kaolinite and illite,the mullite still exists under the temperature of 1 600 ℃,the sanidine disappears at 1 145℃,and the leucite is generated in 1 145-1 286 ℃. Hercynite generated in the system which is composed of pyrite,apatite,calcite,siderite,gypsum and quartz disappears at 1 106 ℃,the hydroxyapatite disappears at 1 455 ℃. When these 8 kinds of mineralsallcoexist,the hydroxyapatite generated disappears at 1 285 ℃,the mullite disappears at 1 118 ℃. After 1 448 ℃,most of solid entersinto the slag. Mullite is a typical refractory mineral in coal,and when the low melting mineral in coal ash becomes the slag,it can react with mullite to generate the low temperature eutectic,and the solid matter content can be reduced,which is good at improving the viscosity-temperature characteristics.