Abstract: 10 MeV/50 kW Ridgetron accelerator is a new type of high-power electron irradiation accelerator. The radio frequence power required in its accelerating cavity is up to one hundred kilowatts. Therefore, a high-power input coupler was specially developed. The coupler consists of ceramic window, inner and outer conductors and coupling loop. The final structure was determined by equivalent circuit analysis and simulation calculation. In order to carry out commissioning of Ridgetron accelerator, a detachable ceramic window and a rotatable coupling loop were adapted in the coupler design. And water cooling channels were designed in the inner conductor, outer conductor and coupling loop to take away the heat generated by power transmission. After testing, the coupling degree of the input coupler can be adjusted in the range of 0 to 2.2, and through it the pulse peak power of 100 kW has been successfully injected into the Ridgetron cavity.