Abstract: The influence of the geometric param eter of the cathode and the width of the trigger pulse on the electron emission from a diode with a ferroelectric cathode was stu died.The PZT samples with different geometric parameter were tested when a positive driving pulse was applied on the samples.The results indicate,when the trigg erelectric field is less than 4kV/mm and the triggerelectric field is stead,the thicker the ferroelectric cathode is,the compacter the fen ce electrodes are,the more they contribute on the emission beam current density.And the emissions due to polarization reversal may exist on the rise-time or the dece nt-time of the trigger pulse.Besides,the best width of the trigger pulse is scale to 150-250ns.