This paper presents a high-efficiency boost converter with voltage clamp function. It clarifies how to design the inductance of the coupled inductor used in the converter, and derives characteristic equations that associate the fluctuation in the input voltage with the output ripple current. For this converter, a theoretical analysis, simulation and experimentation (prototype output: 98 V, 13 A) are performed. As a result, the converter is achieved high efficiency (Maximum efficiency: 98.1%) in the rated output condition, indicating that the voltage stress on the switching power semiconductors can be mitigated by using the voltage clamp function. And it is verified that the snubber circuit can be eliminated in the switching power semiconductors. In addition, the theoretical output ripple current characteristics are corresponded well with simulation and experimental results, and the validity of the design method is proved.