Ultrasonic guided waves have recently been used in fracture evaluation and fracture healing monitoring. An axial transmission technique has been used to quantify the impact of the gap breakage width and fracture angle on the amplitudes of low order guided wave modes í µí±†0 and í µí°´0 under a 100 kHz narrowband excitation. In our two dimensional finite-difference time-domain (2D-FDTD) simulation, the long bones are modeled as three layers with a soft tissue overlay and marrow underlay. The simulations of the transversely and obliquely fractured long bones show that the amplitudes of both í µí±†0 and í µí°´0 decrease as the gap breakage widens. Fixing the crack width, the increase of the fracture angle relative to the cross section perpendicular to the long axis enhances the amplitude of í µí°´0, while the amplitude of í µí±†0 shows a nonmonotonic trend with the decrease of the fracture angle. The amplitude ratio between the í µí±†0 and í µí°´0 modes is used to quantitatively evaluate the fracture width and angles. The study suggests that the low order guided wave modes í µí±†0 and í µí°´0 have potentials for transverse and oblique bone fracture evaluation and fracture healing monitoring.