Abstract: Based on the ultrasonic feature scan imaging and on the feature parameters of ultrasonic reflection echoes from the adhered surface of Al Si thermal barrier coating and the substrate bonding, the debonding defect of thermal barrier coating and the substrate surface can be determined by using the phase characteristics and amplitude characteristics. Samples with coating thickness of 0.5 mm and substrate thickness of 1.5 mm were under testing. The results show that the amplitude of the echo is increased and the phase is also changed obviously. The phase and amplitude characteristics can accurately determine the defects and can also be used for imaging. At last, the accuracy and the sensitivity of the ultrasonic imaging technology to detect the thermal barrier coatings are verified by metallographic experiments.