The split-tapper Balun was introduced in the high-power ultra-wide-band (UWB) antenna. Finite-difference time-domain (FDTD) was used to analyze the Balun and antenna. The 2×4 elements array was fabricated and the measurement result shows that the antenna can resist high voltage up to 250kV with six multiple frequency (200～12 000MHz) and preserves short pulse waveform well. Outdoor detection experiment system was built by using the antenna array. Target detection experiment was carried outdoors. The experiment result indicates that the array can be used in the practical UWB radar for transmitting antenna arrays, thus making a first step for the application of high-power source in radar detection.