Abstract: In this paper，the effect of instantaneous high current impulse on the cathode discharge is verified by the experimental method.Under the environment of higher than 10E^-5 Pa vacuum，the anode structure and the cathode are used to form the triode discharge structure.Value of the high current，colleagues uses the oscilloscope to detect the cathodic electrical parameters of the waveform changes.The study found that an instantaneous current shock above 35A would cause the cathode emission current to drop to 0A within 30ms and then slowly rise to normal values.There is a difference in the impact resistance of the cathodes with different pore diameters，and there is also a difference in impact resistance at different operating points for the same cathode.