The　treatment　of　a　bolt　embedded　in　soil　is　simplified　to　the　model　of　a　rod　embedded　in　an　infinite　medium.　The　dispersion　curves　of　the　model　are　calculated.　Propagation　characteristics　of　longitudinal　modes　in　a　free　bolt　and　a　bolt　embedded　in　soil　are　studied.　The　longitudinal　mode　L(0,1)　in　a　bolt　embedded　in　soil　in　the　frequency　range　from　40kHz　to　90kHz　the　displacement　of　the　profile　is　simple,　which　makes　it　easy　to　be　excited.　Its　attenuation　is　the　smallest　in　all　modes,　and　its　energy　velocity　is　the　fastest.　This　indicates　that　the　longitudinal　mode　L(0,1)　can　be　used　for　the　inspection　of　a　bolt　embedded　in　soil.　At　the　same　time,　the　experiments　on　a　2　in　long　bolt　embedded　in　soil,　inspected　by　using　ultrasonic　guided　wave　have　been　carried　out.　The　results　of　the　experiment　show,　that　the　longitudinal　mode　L(0,1)　in　the　frequency　range　from　40kHz　to　90kHz　is　suitable　for　the　inspection　of　a　bolt　embedded　in　soil.