Considering the lack of scientific and effective methods for testability verification of armament at service stage, we proposed an implementation process of testability verification of armament at service stage based on full demonstration and research. The method for calculating the lower limit of sample size was presented, and data classification and unifying collecting table were given according to different levels of test and maintenance. The method for calculating point estimation and one-sided lower confidence limit was given based on binomial distribution, including the method for evaluating the conclusion of testability verification. Testability data of autopilot and control combination of a certain missile at service stage were taken as an example. Data analysis and conclusion of testability verification were carried out. The result shows that the proposed method is simple, practical and effective for testability verification, which provides a new idea of testability verification of complicated equipment at service stage.