Abstract: A novel UWB horn antenna based on TEM horn structure with wedge-shaped dielectric-filling is investigated. For the wedge-shape dielectric-filling horn antenna, it is found that the radiation energy converged in the dielectric-filling region, thus the radiation field in the direction of the horn axis is improved. Moreover, the appropriate filling of insulating dielectric could prevent the antenna from electric breakdown. The finite difference time domain(FDTD) numerical analysis approach has been adopted to simulate the proposed antenna and the results indicate that it is well suited to high power UWB applications.