Abstract: In this paper, the experimental method of HPM breakdown of coaxialcable and connector is introduced. It is given by experimentaly that the microwave breakdown thresholds of several kinds of coaxial-cables and connectors vary with microwave frequency, pulse width, repetitive frequency and burst duration. Breakdown power threshold increases as pulse width (30 ns~1 μs) decreases, and an inflexion appear at about 100 ns. In low repetitive frequency region, i.e, from single pulse to 1 kHz, the repetitive rate of microwave pulse literally has no effect on breakdown power. Microwave frequency tuned from 2.856 GHz to 937 GHz, no significant change of breakdown power level is observed. When the pulse width becomes as narrow as tens of nanoseconds, the breakdown power varies little even though