Abstract: The bone-conducted ultrasound has been used in hearing aid since finding out that people are able to perceive it. In order to further understand the characteristics of the bone-conducted ultrasound,Finite Difference Time Domain (FDTD) method is used to calculate the sound field in human head model for both unilateral and bilateral stimuli. Simulation results show that bilateral bone-conducted ultrasonic stimulus doesn′t have the ability of source location as common binaural hearing,while the unilateral stimulus can stimulate both cochleae at the same time. The study indicates that the unilateral bone-conducted ultrasonic hearing aid performs better than the bilateral one.