A novel bidirectional DC-DC converter with high conversion ratio is proposed in this paper. The proposed converter uses the coupled-inductor to achieve high voltage conversion ratio. In the boost mode, the proposed converter is cascaded by boost converter and flyback converter with voltage double to increase the voltage gain. The switch voltage stress is reduced by a voltage clamping circuit, and the leakage-inductor energy is recycled. In the buck mode, the circuit consists of asymmetrical half-bridge flyback converter and buck converter. The leakage-inductor energy is recycled by a clamping circuit, and all of the switches achieve zero-voltage-switching turn on. This paper first analyzes the proposed converter operating principles and steady-state circuit characteristics. Eventually, a prototype circuit with conversion voltage 24 V/400 V and output power 500 W is implemented to verify the feasibility of the proposed converter.