Abstract: According to the ultrasonic propagation characteristics and spring model condition,the relationship between the reflection coefficient of bonding interface and incidence angle under once reflection echo was derived,the influence on the reflective properties of bonding interface with the change of bonding material were studied,and the reflection coefficients of weak bonding interface with different stiffness ratio and incidence angle were calculated.Numerical simulation results show that when oblique incidence wave is S-wave,there is a critical angle,and the reflection coefficient changes greatly under the critical angle;critical angle varies with the changing of the upper material,and the reflection coefficient reaches the minimum under the critical angle;when debonding,with the increase of the critical angle,the minimum reflection coefficient decreases;for the weak bonding interface,with the stiffness ratio decreases,the reflection coefficient drifts upward when the incidence angle is smaller than a certain angle.