Energy security is an eternal topic of Japan's domestic affairs and diplomacy, so Japan's energy policy always takes energy security as the core target. With the gradually development of energy problem and the time request, the connotation of energy security is changing, and Japan's energy policy also has been revised and adjusted. The Fukushima nuclear accident poses challenges to Japanese traditional concept of energy security, to ensure the safety of the energy use has become an important goal of Japan's energy policy. The basic direction of Japan's energy policy in the future is determined by keeping the balance among four targets such as "stable supply", "to cut supply costs", "low carbon" and "to ensure that energy use security". <<