Abstract: This paper describes a study on inspection of bonding defects in metal honeycomb structures by mechanical impedance method. It covers principle, structures of probes and instrument, experiments in which artificial defects are detected and results, and application to production process. Conclusion is that the sensitivity and reliability of the method satisfies the related specifications. This paper points out the advantages and disadvantages of mechanical impedance method and the difference in application between probe having two contactors and probe having one contactor.