In the process of pasting the heating plate, due to improper operation, defects such as bubbles, delamination and inclusions will appear in the bonding layer. These defects lead to uneven heat transfer of the heating patch, causing heat accumulation. And then the heating wire in the heating patch is burned out, which eventually leads to the heating patch failure, seriously affects the normal operation of the equipment, and even scrapes the whole equipment. Therefore, it is very necessary to carry out comprehensive nondestructive testing before the equipment is put into use. There are many ways and methods of non-destructive testing. In this paper, non-destructive testing is carried out for the bonding quality of heating patch, and the testing effects of one-side pitch-catch technique of air-coupled ultrasonic, opposite pitch-catch technique of air-coupled ultrasonic and terahertz testing method are compared and analyzed. The results show that the THz nondestructive testing method has a good detection rate for the internal defects of the bonding layer of the heating patch, and the experimental study provides an effective method for the detection of the internal defects of the bonding layer of the heating patch.