Power electronic traction transformer (PETT) is a new topology for a traction drive system, which can realize the high voltage and power conversion through multilevel converters and high-/medium-frequency transformer link. Reliability becomes a key issue for PETT adopting the module-cascaded structure. In this paper, an improved fault-tolerant method based on reverse-charging control of dual active bridge is proposed, which is suitable for PETT and other two-stage structure converters. The control strategy and operating process of an improved fault-tolerant method are introduced. Comparisons among improved and traditional fault-tolerant methods are also presented. Simulation and experimental results are provided to show the correctness and effectiveness of the improved fault-tolerant method.