In guided wave inspection, dispersion curves and wave structures are basis for designing tools and analyzing waveforms. First, this paper deals with a semi-analytical finite element method (SAFEM) for modeling wave propagation in elastic waveguides of arbitrary cross-section and describes solutions of the dispersion curves and wave structures with this numerical methods. Then the vertically vibrating mode guided waves dispersion curves and wave structures for U60 rail are obtained using semi-analytical finite element method and discusses the application of the dispersion curves and wave structures in guided wave inspection for railhead defect. Finally, instrumented hammer experimental study and jointed time-frequency analysis were carried out to verify the vertically vibrating mode guided waves dispersion curves numerical results. FEM modeling and experimental investigations of railhead transverse defect detection shows that the vertically vibrating mode guided wave was suitable to inspect the defect in railhead.