Modern　signal　processing　has　been　playing　an　more　important　role　in　ultrasonic　guided　waves　of　nondestructive　testing　and　evaluation.　To　demonstrate　how　to　improve　the　readability　of　guided　waves　signal　and　enhance　the　ability　of　defection　identification,　a　review　and　comparisons　of　some　methods　including　time-frequency　representations,　wavelet　analysis,　Hilbert-Huang　transforms,　and　cross-correlation　techniques　and　so　on　have　been　carried　out.