To get ultra-wideband and large power terahertz waves, ultra-wideband terahertz sources space power synthesis fundamental based on time domain waveform is put forward. Space power synthesis simulated experiment based on multi-channel latency and waveform transform is carried out with standard data, and related data of terahertz wave space power synthesis is obtained. The simulated experiment indicates in physical experiment of ultra-wideband terahertz sources space power synthesis there can be a certain delay from femtosecond laser to leading edge of every photoconductive antenna unit. During optimization design and the fabrication processing of photoconductive antenna, special attention should be paid to decrease the error of rising edge of terahertz.