Abstract: This paper studies a high power radio-frequency combiner based on rectangular cavity power combination. The combiner can achieve direct coupling with the power amplifier modules, with high combining efficiency, large power capacity, and adjustable power capacity, which can well meet the current CiADS requirements for the gradient of the power capacity of solid state amplifier. The simulation results of the 12 in 1 combiner show that the amplitude and phase transmissions of each input port to the output port have good consistency, maximum deviation within 0.05 dB and 0.5° respectively. The power capacity of the solid state amplifier can be adjusted by changing the number of power amplifier modules.