Abstract: In this paper, by using the thermal image technology, we detected the ammonia plants gasifier of a fertilizer plant through using the infrared camera of model PM290E and then using special software to capture images for analysis. Based on heat transfer theory we calculated the surface temperature of the gasifier wall. On this basis, we proposed a fault diagnosis theory based on infrared detection, and then we realized the failure defection analysis and evaluation. Now it proved that the proposed method of infrared thermal imaging could be a good failure analysis and diagnosis, which could provide a good guide for the safe operation of the gasifier.