To solve the problem that the couplant can't be used on the surface of SRM shell bonding structure in ultrasonic detection, a dry-coupled ultrasonic detection system is built, and then special-structure piezoelectric vibrator and transmission rod are designed for dry-coupled probes. Based on the time reversal, a dry-coupled ultrasonic imaging method is proposed and the time reversal principle is analyzed. The transient fluctuation chart on the focus moment is established by extracting damage scatter signals, time reversal and secondary loading. Finally, the defect images are obtained by two methods, including the sum and the product of the amplitudes of signal elements. The experiment shows that the proposed method is valid to detect the shape and the position of the defect in bonding structure.