Abstract: The coal ash content in Shendong Mining Area is low,and the fluctuation of mineral composition has a great influence on the viscosity-temperature characteristics of coal ash,especially the viscosity of coal with high Si/Al is generally high at high temperature,resulting in serious slag plugging problem in the gasification process. Through the float and sink analysis,the main mineral composition of Shendong Coal Mine was quantitatively analyzed by using SEM. The viscosity-temperature curve of coal ash was measured by using high temperature coal ash viscosity tester. The viscosity-temperature characteristics of coal ash were simulated by Factsage 7.3 based on its composition. The results show that:the mineral composition of samples in Shendong Mining Area is mainly illite clay mineral (20%～70%),calcite (6%～34%),pyrite (2%～10%),siderite (3%～50%),and some clastic quartz (6%～24%) coexists with illite; the high content of illite and some associated quartz result in high Si-Al content and Si/Al ratio of samples,the Si-Al content in coal ash components is 50%～75%,and the Si/Al ratio is between 2.3 and 3.1,which is the main reason for the high viscosity of the coal ash in Shendong.; calcite is the main calcium mineral in the sample,which is filled in the cracks of coal or structural pores of organic matter components. Due to the depolymerization and destruction of the melt network by calcium ion at high temperature,the high Ca content will lead to relatively low viscosity; In addition,the iron series minerals are mainly sulfide minerals pyrite and carbonate minerals siderite. The relatively high Fe content leads to more divalent iron ions connected with six oxygen atoms to form octahedral structure,resulting in loose network structure,which will also reduce the viscosity of coal ash to a certain extent. The simulation results after mixing four kinds of commercial coals in Shendong Mining Area show that the optimal coal ash ratio is between 4∶6 and 7∶3,and the coal sample ratio is between 4.1∶5.9 and 8.3∶1.7,which can better meet the operating temperature and viscosity range of liquid slag discharge gasifier.