Abstract: In this paper, the shortcoming for the fixed-duration test plans in MIL-HDBK-781 and IEC61124 （2002） draft are pointed, and a new class of fixed time/failure terminated test plans with two stages is proposed. For each plan in the new class, the difference between the practical risk and nominal risk is not exceed 5 × 10^-4 and the less total test time is needed. Meanwhile, a detailed algorithm and a software are provided to calculate the confidence limit of reliability parameter θ（MTBF） for all test plans of the new class.