In this paper, a novel high step-up dc-dc converter with coupled-inductor is proposed. The proposed converter utilizes a coupled-inductor and a voltage doubler to achieve high step-up voltage gain. The voltage stress of power switch is reduced by a passive clamp circuit. Therefore, low resistance ROS(ON) of the main switch can be able to reduce conduction loss and the conversion efficiency is improved. The operating principle and steady-state analyses of voltage gain are discussed in detail. The experimental results show the voltage stresses of power source and diodes, the currents of leakage inductor, secondary-side of coupled inductor and diodes. Finally, a prototype circuit with 24-V input voltage, and 400-V output voltage, and 200-W output power is implemented in the laboratory to verify the performance.