Abstract: We provided an analytical study of ultra-wideband pulse spatial power combination in time domain, and got the conclusion that the multiplex pulses which had the same polarization direction and unified waveform got the maximum output power. And based on that, a linear-array fed parabolic cylinder antenna was proposed. A line array of 10 tacked TEM horns was arranged in the focal-line, which formed 10 coherent beams after illuminating the reflector. An UWB high power microwave beam on boresight was achieved by coherent superposition of these beams. Simulation results showed that compared with the single-fed antenna with the optimalaperture, the designed antenna increased the radiated power density up to 87 times, and decreased the combined beam width from 66to 8. Ultra-wideband high-power microwave pulse synthesis was realized effectively through spatial power combination.