This paper presents an active clamped current-fed full-bridge converter integrating LLC converter for fuel cell power system. In the proposed converter, the half-bridge LLC converter is integrated into the conventional active clamped current-fed fullbridge (ACCF) converter without additional active components and volume increasing. The proposed converter has a low voltage stress on the primary switches because a high step-up voltage conversion ratio can be realized with the low duty ratio D. In addition, due to two transformers structure, the conduction loss of main switches (S1-S4) is decreased by reducing of the peak current. Moreover, the turn-off and conduction losses of auxiliary switch (Saux) are reduced by sinusoidal shape resonant current of the LLC resonant tank. To verify the performance of the proposed converter, the prototype converter with 36V-57V input and 400V/1kW output is implemented.