Since the solid rocket motor interface bonding is prone to debonding during its storage， ultrasonic longitudinal wave is used to detect the bonding quality of the first and second interfaces， the second interface debonding defect signals are usually mixed with multiple reflection and transmission signals of the first interface， resulting in that it cannot be distinguished from the bonding signal of the interface. To distinguish the echo signals of different interfaces， EMD （Empirical Mode Decomposition） is first used to decompose the echo signal and get the dominant modal component of the signal according to the correlation coefficient， then the interface bonding situation is obtained by extracting amplitude characteristics of the detected signal， finally， whether the bonding position is the first interface or the second interface can be determined according to the time. The results show that the features of ultrasonic echo signals extracted by EMD can realize the detection of debonding defects with a minimum diameter of 4mm in the solid rocket motor interface， besides， EMD can reduce the data quantity of analysis and calculation effectively， providing a certain basis for solid rocket motor bonding detection.