The coal ash melting deformation temperature (DT), softening temperature (ST), flow temperature (FT), and commonly used softening temperature (ST) obtained under specified conditions that vary with heating temperature. The higher the coal ash melting temperature, the less likely the coal ash is to form slag. Due to different boiler designs, the requirements for ash melting temperature are also different. The melting temperature of coal ash directly affects the performance of coal as fuel and gasification raw material. Low melting temperature of coal ash makes it easy to form slag, which increases the difficulty of slag discharge. Especially for boilers with solid slag discharge and gasification furnaces with moving beds, high melting temperature of coal ash is required.