In　order　to　investigate　the　attenuation　characteristics　of　ultrasonic　longitudinal　guided　waves,　first,　the　characteristics　of　longitudinal　modes,　such　as　dispersion　and　multi-mode,　for　centre　and　peripheral　wires　in　steel　strands　are　analyzed　theoretically.　In　the　experiment,　the　lowest　longitudinal　mode　of　ultrasonic　guided　waves,　L　(0,　1)　mode,　is　excited　by　piezoelectric　thickness　vibration　element　and　received　by　developed　magnetostrictive　sensor　in　a　seven-wire,　17.80　mm　nominal　diameter　steel　strand.　In　a　traction-free　steel　strand,　with　the　increase　of　frequency　in　the　range　of　110　kHz-160　kHz,　attenuation　of　L　(0,　1)　mode　will　decrease.　Furthermore,　in　a　steel　strand　embedded　in　cement,　with　the　increase　of　embedded　lengths,　L　(0,　1)　mode　amplitudes　decreases.　The　results　provide　experimental　foundation　for　the　analysis　of　inspection　ability　to　steel　strands　using　longitudinal　modes　and　the　application　of　ultrasonic　guided　waves　technique　to　health　monitoring　of　steel　strands.