The invention discloses a high-frequency cavity radio-frequency breakdown protection device comprising an analog comparator, two detecting, sampling and holding circuits, a linear amplifier, and a waveform identification unit. The two detecting, sampling and holding circuits are respectively a detecting, sampling and holding circuit A and a detecting, sampling and holding circuit B, wherein the input end of the detecting, sampling and holding circuit A is connected with an incident signal end, the output end of the detecting, sampling and holding circuit A is connected with the linear amplifier, the output end of the linear amplifier is connected with the inverse-phase input end of the analog comparator, the input end of the detecting, sampling and holding circuit B is connected with a reflected signal end, and the output end of the detecting, sampling and holding circuit B is connected with the in-phase input end of the analog comparator. The output end of the analog comparator is connected with the waveform identification unit. The waveform identification unit includes a radio-frequency breakdown type identification unit and a radio-frequency breakdown protection unit. Based on the principle, high-frequency cavity radio-frequency breakdown signals can be collected and analyzed, the number of times of high-frequency cavity radio-frequency breakdown can be controlled, and reduction of average beam current intensity is avoided.