Aims at the safety problems caused by corrosion under coating for it can not easily be observed, specimen of corrosion damage under coating was made for the research of detection by applying infrared thermal wave technology. The surface temperature distribution infrared thermal images were captured, also the surface temperature history of corrosion area, non-corrosion area and their difference. Analysis of test results show that the infrared thermal wave technology is an effective tool in detecting corrosion damage under coating, there has a fine detection time used to estimate the coating thickness, and the position and sizes of defects can be found out directly by the hot spots in the infrared images. The damages can be quantitatively recognized by images processing, but surface uniformity of the specimen has great impact on the damage identification.