The debonding of the coating layer easily causes the local stress concentration of the charge column, which affects the normal combustion of the charge column, and causes serious safety hazards in its operation. In view of the structural poor performance and low durability caused by delamination and degumming of adhesive interface in the process of processing or service of the drug column structure, this paper studies the different kinds of defects preset in the adhesive structure based on the digital knock detection theory, and finds that the debonding elastic coefficient K2 directly affects the degree of debonding defects, The results show that the dynamic module in ANSYS is used to simulate the knock detection model. The stress duration extracted from the data results defines the influence of different factors on the bonding quality of the coating. The experiment shows that the detection ability of knock will have correlation effect on the size, depth, position and angle of local defects in the structure.