Ultrasonic　Lamb　wave　technology　holds　extreme　significance　in　the　structural　health　monitoring　of　integral　metal　wall　plates.　However,　its　application　is　limited　due　to　complex　Lamb　wave　transmission　characteristics　caused　by　stiffeners.　In　the　study,　the　transmission　characteristics　of　Lamb　waves　in　common　types　of　stiffener　cross　sections　(I-type　and　Gamma-type)　of　large　wall　plates　were　investigated.　A　2D-FFT　(Two-Dimensional　Fast　Fourier　Transform)　calculation　method　was　developed　to　accurately　analyse　the　transmission　characteristics　of　Lamb　waves　in　stiffened　plates　with　different　stiffener　cross-sections.　The　stiffener　structure　could　be　considered　as　a　comb　filter　through　the　experimental　and　simulation　results.　Theoretical　and　experimental　evidence　shows　that　the　characteristics　of　the　filter　are　mainly　affected　by　the　dimensions　of　the　height　direction　of　the　stiffeners.　The　variations　of　comb　filtering　characteristics　of　Lamb　waves　with　stiffener　geometry　were　deeply　analysed.　In　addition,　the　formation　mechanism　of　the　comb-filtering　effect　of　the　stiffeners　on　the　transmitted　wave　has　been　validated　through　experimental　measurement.　This　study　provides　the　basis　for　the　reasonable　frequency　selection　of　Lamb　waves　for　detecting　the　stiffened　plate　structure,　and　it　significantly　advances　the　application　of　Lamb　waves　in　the　structural　health　monitoring　of　integral　metal　wall　plates.