Abstract: Two kinds of graphite cathode (normal graphite cathode and copper-graphite cathode) are used in the electron microscope experiment and the repetitively long-pulse experiment separately. The experimental results show that microstructures of the two graphite materials are obviously different, and the copper-graphite is little better than the normal graphite in the explosive emission performance of cathode, pulse width and stability of the repetitively long-pulse high-power microwave. Those experimental conclusions are still needed to be confirmed in the future.