DC Transformers are the key device in the development of DC distribution. For the multiple modular high frequency link DC transformer (DCT), the value design methodology of series inductor and DC capacity is presented in consideration of the switch safety and the output voltage ripple. Then the DCT under single phase shift is analysed,and the characters of operation and harmonic symptom are derived. The numerical model of DCT is presented, and the flow chart of DC transformer numerical simulation computation is given. Finally, a prototype is built based on the aforementioned method, and the comparison between prototype and numerical simulation is achieved. The results verify the correctness and effectiveness of the theory in this paper.