Abstract: Aiming at the problems of large size and high cost of DC transformers, the isolation stage hybrid three-level bidirectional LLC-DCT topology was proposed. This topology has the characteristics of high bus voltage level, which reduced the number of modules number of DC transformer system and reduced its volume and cost. This topology used the equivalent pulse-spread generation method to achieve energy bidirectional flow and full range soft-switch as well as voltage equalization of series devices. The modal analysis and theoretical study of the method were carried out, and analyzed the gain characteristics and the conditions that need to be met for soft-switch and series device voltage equalization. Finally, the simulation platform and a 3 kW 1 kV-280 V module experimental prototype were built respectively. The simulation and experimental results show that the voltage gain deviation of this method is less than 1%, the bi-directional zero voltage switching（ZVS） and quasi-zero current switching（ZCS） can be realized, and the non-uniformity of series devices is less than 1%.