Abstract: The research on ultrasonic guided wave scattering characteristics on rail base oblique cracks is the basis of the appropriate guided wave detection technology. This paper includes numerical analysis result of the guided wave propagation characteristics on rail base and the effects of different excitation frequency on it. Based on ABAQUS software, a finite element model of the rail base is established at different angles, which is used to analyze scattering characteristics of transverse and vertical vibration mode wave in the rail base at different angles .The numerical analysis results and wave field simulation snapshots show that frequency dispersion phenomenon of transverse vibration mode wave on rail base oblique cracks is more obvious than that of vertical vibration mode. It is therefore the vertical vibration mode rather than the transverse one that can give better detection effect. This study also provides a theoretical basis for the subsequent rail base guided wave detection experiments.