The　attenuation　dispersion　curve　and　group　velocity　dispersion　curve　of　ultrasonic　guided　waves　in　steel　rod　are　calculated　with　consideration　of　the　attenuation.　Propagation　characteristics　of　high　frequency　longitudinal　modes　between　1　MHz-3　MHz　in　steel　rod　are　studied.　In　theory,　there　is　one　attenuation　minimum　in　every　high　order　longitudinal　mode　whose　attenuation　is　the　smallest　in　all　modes　at　the　special　high　frequency.　The　high　order　mode　at　this　special　frequency　can　propagate　a　longer　distance　than　other　modes　at　the　same　frequency.　This　indicates　that　high　frequency　low　attenuation　longitudinal　mode　at　this　special　high　frequency　can　be　used　for　the　inspection　of　steel　rod.　The　experiments　on　steel　rod　of　22　mm　in　diameter,　2　m　in　length　are　carried　out　using　ultrasonic　guided　wave.　Guided　wave　signals　are　excited　and　received　by　the　same　probe　at　the　same　end　of　the　rod.　The　group　velocity　and　amplitude　curves　of　first　end　reflection　against　frequency　are　obtained.　The　experimental　curves　are　consistent　with　those　dispersion　curves　of　theory.　This　indicates　that　the　dispersion　curve　of　steel　rod　with　consideration　of　attenuation　characteristics　can　be　a　guidance　to　experiment.