The invention specifically relates to a high-efficiency large-power microwave space power synthesis method. A device comprises a main unit module, a battery module, and an antenna module. The main unit module includes an interface, and the main unit module is electrically connected with the battery module and the antenna module through two interfaces in an integrated manner, and the antenna moduleuses beams radiated by multiple antennas to perform power synthesis in a space. According to the invention, the main unit module is electrically connected with the battery module and the antenna module through two interfaces in the integrated manner, so the installation, maintenance and use are simple, and the maintenance is facilitated. The antenna module can complete the detection foo a non-cooperation target, also can achieve the space power synthesis at a target position, and obtains a large-power microwave. The method is simple and easy to implement, and is high in power synthesis efficiency.