Abstract: Using ultrasonic guided wave to assess long bone fractures and fracture healing has become a promising diagnostic issue. But the multiple guided wave modes alias has always been a big challenge. To solve this problem, a low frequency signal is used in the two-dimension finite-difference time-domain (2D-FDTD) simulation and only SO and A0 modes are excited. The amplitudes of guided waves SO and A0 in long bone with different fracture width and angle are analyzed. The results show that both SO and A0 amplitudes decrease with the increasing of fracture width in different oblique fracture angles. A0 amplitude increases with the increasing of oblique fracture angle while SO amplitude decreases with the increasing of fracture angle then increases with the further increasing of fracture angle with a turning point at around 45°. The ratio parameter between the amplitude of SO and A0 can evaluate the change of fracture width in different fracture angle cases. Thus, it can provide basis for evaluating fractured long bone with vertical and oblique angle and monitoring the healing of fractured long bone.