Based　on　the　principle　of　ultrasonic　testing,　the　non-contact　ultrasonic　time-domain　simulation　testing　method　was　developed　for　the　debonding　and　weak　bonding　defects　of　composite　structures.　Firstly,　the　time-domain　simulation　model　of　the　ultrasonic　transmission　characteristics　of　single-layer　CFRP　(carbon　fiber　reinforced　polymer)　plate　is　established,　and　the　frequency　spectrum　of　the　transmission　coefficient　is　obtained.　By　comparing　with　the　plane　wave　theory,　the　results　show　that　the　simulation　results　are　in　good　agreement　with　the　theoretical　calculation.　Then,　the　ultrasonic　transmission　coefficient　of　single　/　double　interface　weakening　and　cohesive　weakening　in　composite　bonding　structure　is　simulated.　The　simulation　results　show　that　with　the　decrease　of　interface　stiffness　and　the　deepening　of　cohesion　weakening,　the　local　extreme　points　in　the　transmission　coefficient　spectrum　tend　to　shift　to　the　low　frequency　side,　and　the　offset　of　the　extreme　points　caused　by　the　decrease　of　spring　stiffness　is　different　at　different　frequency　points.