Abstract: The temperature of the bottom surface of a tundish was calculated by using an one-dimensional steady-state heat transfer model. The relationship between the temperature of the bottom surface and the damage degree of the tundish lining was established. It was found that the temperature rises with the increase of damage degree. Practical examinations proved that the temperature of the bottom surface rises with the increase of tundish age, and both the detection of damage degree and the quantitative analysis of tundish lining can be carried out by the infrared image technology.