The invention discloses an insulation layer debonding damage monitoring method based on ultrasonic guided waves. The insulation layer debonding damage monitoring method comprises the following steps: an excitation end and a corresponding receiving end for receiving an ultrasonic guided wave signal are arranged by arranging an excitation sensor array on a to-be-monitored structure, an ultrasonic guided wave echo signal collected in a complete insulation layer bonding state is taken as a reference signal Em', and an ultrasonic guided wave echo signal collected in a to-be-monitored state is taken as a monitoring signal Em''; and the shannon entropy of the reference signal Em' and the monitoring signal Em'' is calculated respectively, and an absolute value of the difference of the shannon entropy is taken as a debonding coefficient Dm for evaluating the bonding condition. According to the insulation layer debonding damage monitoring method, the detection efficiency of the traditional single-point nondestructive testing is increased through large-area structure detection capacity of the ultrasonic guided waves, and on-line real-time insulation layer debonding monitoring is achieved.