Abstract: As hollow cathode is the primary electron source for Ion thruster discharge chamber plasma ionization and also for electron beam neutralization,its ignition reliability directly affects the reliability of thruster operation.This paper depicted the evaluation of the reliability of ignition under the expected life of the hollow cathode by taking 20 cm ion thruster in orbit cross-section as an example.By using the method of a small sample of the reliability testing and combination of reliability assessment theory,the results were obtained that between confidence intervals 0.9 to 0.95,hollow cathode ignition reliability is better than 0.98 when LHC-5 hollow cathode ignition times reaching 6 000 times.The results proved that the reliability of the hollow cathode of LHC-5 meeting the requirements of space applications.The research results showed positive significance to reliability growth design of hollow cathode and research in reliability evaluation method of electric propulsion products.