Abstract: The test data of system and its units are provided through the reliability test of weapon. At the stage of approval test, the common evaluation method is to take the system test time into account but not considering the units test time, and the failure number in units test is either added directly into the total failure number (very severe but unscientific) or discarded (information waste). Based on the reliability model of exponential series system, the failure number and total time of units test are converted into the equivalent failure number and time of system by introducing the approximation formula of fiducial probability density of failure rate under fixed time truncated test scheme. The result indicates that the units test data can be used to supplement the system test data, reduce the cost of test, and improve the evaluation accuracy of reliability. The result also shows that the conversion formula of units data of fixed number truncated test is different from that of fixed time truncated test, and applying mechanically the conversion formula of fixed number truncated test is not worth advocating for the fixed time truncated test. Key

Key words: weaponsystem, reliabilityevaluation, fixedtimetruncatedtest, exponentialseriessystem, unitstestdata, systemtestdata, conversionformula