Abstract: In order to solve the problem of microwave ignition of solid energetic materials under low power conditions, this paper proposes a low-power high-field microwave ignition technology based on dual-focusing optimization design of rectangular resonant cavity. The developed microwave ignition device consists of a solid-state microwave source, a rectangular resonant cavity, a microwave probe and other components. Among them, the rectangular resonant cavity is fed by a probe, and the energy is focused once by resonance. Combined with the distortion effect of the probe tip on the electric field and the compression effect of the metal stage on the electric field distribution space, the secondary focusing of the energy in the cavity during resonance is achieved, and the electromagnetic compatibility design is used to prevent electromagnetic wave leakage. The simulation and experiment show that the microwave ignition device has multiple operating frequency points in the range of 2−3 GHz and the frequency is adjustable. The maximum field strength can reach MV/m level at 22 W power, enabling effective ignition of small black powder. Compared with the existing device, the ignition power is significantly reduced. The developed low-power and high-field microwave ignition technology can provide a platform for the study of microwave ignition of solid energetic materials.