It is difficult to obtain effective bonding defects characteristics from the main echo of terahertz pulse when the defect thickness is too small, because the terahertz time-domain pulse carrying the defect information overlaps with the reflection pulse from the substrate. To this end, a terahertz propagation model based on transfer matrix method is established. The model is used to numerically analyze the propagation characteristics of terahertz pulse in the bonding defects of thin coating. Combined with the terahertz time-domain simulation results of coating bonding defects, a method for identifying coating bonding defects based on multiple echo features is proposed, and the skewness characteristic of defect signal is used to construct terahertz image. The 10- and 15-μm-thick bonding defects preset in 50- and 80-μm-thick coatings are identified successfully with an average recognition accuracy of 95.2%.