It is better to use castable with Al2O3 content of 62%~66% as permanent lining of tundish, which is mainly composed of mullite and has good thermal shock resistance. As far as slag resistance is concerned, it is better to have a higher Al2O3 content, but for Al2O3-SiO2 raw materials, the higher the Al2O3 content, the greater the expansion and the worse the thermal shock resistance. Therefore, in order to ensure the thermal shock resistance, the Al2O3 content of castable needs to be controlled. Using ultra-low cement bonding technology, the cement content is low, and the Cao-Al2O3-SiO _ 2 low melting point phase substances formed at high temperature are very few. The influence of castable properties on thermal shock resistance, the smaller the ratio of high temperature fired strength to medium temperature fired strength, the better the thermal shock resistance of castable. Therefore, for the thermal insulation project being implemented, in addition to setting the thermal insulation layer at the steel shell, light permanent lining castable should also be used, and the strength should be controlled, so as not to excessively pursue low thermal conductivity. Table 4 below is the measured performance index of light permanent lining castable.