This paper is intended to acknowledge the Japanese effort of against nuclear test by North Korea and Japanese government‟s action on civil protection which considered threats to Japan security and regional security.. This writing is focus on the effort of Japanese Government on handle the threat of nuclear test by Korean Utara to protect the civilization without violating the rules that binds Japan. Nuclear test by Korea Utara become a concern for the world, also become serious threat for regional era especially for Japan. With the strategy that taken by Japan, Japanese Government used a defense strategy in the form of J-Alert system. This system will response if there are a missile launch that likely to pass through the Japanese area as an early warning system.