Abstract: It is difficult to ensure effective detection for crack defects because of the influence of blade structure and coating state in the fluorescence detection of aero engine coated hollow blades. According to the principle of ultrasonic infrared detection technology, 2 hollow specimens without coating and 3 hollow specimens with coating are detected respectively, and fluorescence detection is also performed for the specimens at the same time. Compared with the detection results of the two methods, inconsistent results are found when detecting the hollow specimens with coating. After further microscopic observation, the existence of the cracks detected by ultrasonic infrared detection was verified, which are missed in the fluorescence detection results. The experimental results show that the ultrasonic infrared detection technology is less affected by the blade structure and coating state, and can detect the inner and outer surface cracks of the coated hollow blades more effectively.