This paper presents a topology of cascode scheme that is different from traditional cascade circuit. A high-efficiency cascode forward converter is proposed, with high voltage gain, low leakage impedance and same control method as conventional converter. In fuel cell system can use the characteristic that compensate the polarization loss of cascode circuit to achieve a steady output voltage. The operational principle and steady-state analysis are described. Finally, a simulation result with a 480W system output, 20V-38V fuel cell DC input and 48V DC output is presented to demonstrate the performance. It shows that the efficiency of the proposed converter is nearly 96%.