In order to reduce the volume of the multi-pulse rectifier, this paper proposes a 12-pulse rectifier based on power electronic phase-shifting transformer (PEPT). In the proposed topology, the power frequency AC voltage is converted into the high-frequency voltage by a power electronic converter. The high-frequency voltage is then phase-shifted by a high-frequency phase-shifting transformer and sent to the input terminals of two sets of three-phase rectifier bridges to complete the rectification process. After analyzing the works of the power electronic phase-shifting transformer and studying the working modes of the three-phase diode rectifier bridge, we derive the expression of the input current and the load voltage. Simulations and experiments have shown that the proposed topology can reduce the transformer's volume to less than one-third of the power frequency transformer, improving the transformer power density. Furthermore, it can maintain the same input current quality and ensure the stability of the rectifier device, which verifies the correctness and feasibility of the theoretical analysis.