In　order　to　detect　the　defects　of　inner　and　outer　surfaces　of　thick-walled　pipes,　a　Rayleigh　waves　flexible　transducer　with　non-equal　interval　comb　is　designed.　Firstly,　an　optimization　design　method　based　on　the　concept　of　mutual　admittance　is　proposed,　and　the　amplitude　frequency　characteristics　of　Rayleigh　waves　transducer　with　equal　interval　comb　are　optimized.　The　influence　of　the　key　parameters　such　as　the　array　element　interval,　the　width　of　the　array　element　and　the　number　of　elements　on　the　waveform　and　amplitude　of　the　received　signal　are　analyzed　by　using　the　finite　element　method.　Based　on　the　analysis　of　the　mutual　admittance　principle　and　time　frequency　analysis,　it　is　determined　that　the　optimal　element　interval　is　equal　to.R,　the　element　width　is　lambda(R)/2,　and　the　elements　number　is　5.　Finally,　based　on　the　conclusion　of　equal　interval　transducer,　the　non-equal　interval　comb　transducer　is　designed　to　obtain　a　good　Rayleigh　wave　signal,　which　provided　a　good　foundation　for　the　practical　manufacture　and　experiment　of　the　transducer.