A Bayesian reliability assessment method for cartridge of ejector was proposed. The reliability information of whole cartridge and its subsystems was comprehensively utilized in this method. Firstly, inheritance factor was determined, then mixed Beta distribution was established based on the reliability information of whole cartridge and its subsystems, lastly, the posterior distribution was used to assess system reliability. With new method and GJB376-1987 method and the traditional Bayesian method, the reliability of a cartridge ejector was respectively evaluated to reach 0.9922, 0.978, 0.996 under the confidence level 0.90. The result shows that the new method is effective to evaluate the reliability of cartridge of ejector.