Abstract:Research Work on electron optics system of multi-beam klystron has been described systematically in this paper.Design consideration and design methods for periodic reversal permanent magnet focusing system are presented ,special technical problems met in design of multi-beam electron gun with controlling electrode are discussed.2D computer software or magnetic field and electron trajectory of electron optics system has been established,and applied to calculate the electron optics system of S-band 200 kW multi-beam klystron.This multi-beam klystron has output power of 180kW,bandwidth of 7.6%,efficiency of 44.4%,gain of ggreater than 45dB,DC beam transmission of 89%.RF beam ransmission of 69~83%.There is good consistence between experiment and calculation.