Abstract: The propagation characteristics of the repetition-rate high-power microwave (HPM) in atmosphere were studied theoretically, and the electron density expression at a point in atmosphere was educed after HPM pulses transmitting. The relationship between the number of the penetrated pulses and the microwave power was described under different atmospheric pressure and microwave pulse parameters. The simulation results indicate that the smaller the atmospheric pressure is, the smaller the number of the penetrated pulses is when air gets breakdown at the same microwave pulse parameters, and the wider the pulse width and the lower the microwave frequency, the smaller the number of the penetrated pulses.