The　experimental　study　of　ultrasonic　transmission　coefficient　measurement　method　was　carried　out　for　the　problem　of　bonding　quality　inspection　of　bonded　structures　of　composites　with　thick　adhesive　layer.　For　the　uniaxial　CFRP　bonded　specimens,　the　ultrasonic　waves＇　phase　velocity　distribution　and　the　ultrasonic　transmission　coefficient　spectrums　were　measured　by　the　water-immersion　ultrasonic　transmission　method.　Then　their　complex　elastic　constants　were　inversed　by　the　particle　swarm　optimization　algorithm　based　on　simulated　annealing.　Based　on　this,　CFRP　bonded　specimens　in　perfect　bonding　status　and　having　single　weak　bonding　interface,　dual　weak　bonding　interfaces　were　manufactured.　Then　the　ultrasonic　transmission　coefficient　spectrums　were　measured,　and　the　distinction　of　bonding　quality　between　different　bonding　specimens　was　predicted.　At　the　same　time,　according　to　the　shift　characteristics　of　the　measured　ultrasonic　transmission　coefficient　spectra,　the　influence　of　the　symmetry　of　the　CFRP　bonded　structures　with　thick　adhesive　layers　on　the　ultrasonic　transmission　coefficient　spectrums　was　investigated　experimentally.　In　addition,　by　comparing　the　time-domain　and　coefficient　spectra　characteristics　of　transmitted　waves,　the　advantage　of　using　the　coefficient　spectrum　measurement　method　in　bonding　quality　detection　was　expounded.