Abstract: Based on the sound field characteristics of steel-rubber bonding parts, an air-coupled ultrasonic C-scanning system was built by using the air-coupled longitudinal wave penetration method, which solves the problems of difficult coupling and high requirements for inspectors in practical engineering applications.The air-coupled ultrasonic flat probe with a frequency of 200 kHz was used for the C-scan imaging detection of the artificial debonding defects in the steel-rubber bonding parts (steel plate thickness 5 mm, bonding layer thickness 1mm, rubber thickness 4mm)in the range of 120 mm×90 mm. The imaging results show that this method can identify the smallest debonding defect of φ6 mm, and the outline of the defect of φ10 mm can be clearly displayed, which effectively solves the non-destructive testing of steel-rubber bonded parts.