During the implementation of environmental policy, it often encounters unexpected policy barriers. It causes significant problems on the effectiveness and efficiency of the environmental policy implementation. Among various reasons, it is one of the most important reason that two stages of environmental policy making and implementation process are often separate. Therefore, We should approach this issue with the idea of intergovernmental relations. With these policy environment and characteristics, this article studies the policy effectiveness of environmental policy implementation emphasizing on the role of public prosecutors office as an important policy actor. This study shows that public prosecutors office is becoming one of the most important policy actors in the environmental policy implementation in the era of local autonomy system. Its public prosecution by the strict adoption of environmental law improves the policy effectiveness and efficiency of environmental policy implementation. Many studies have been done on the policy key actors. However, this study has two valuable strength: one is that it focuses n the policy implementation process and the other is that it studies on the public prosecutors office as a policy actor which has not been done much. The research on the role of local prosecutors in policy making is necessary in the carly settlement stage of local autonomy. With this kinds of study researches on the intergovernmental relations among central and local governments, courts in policy making should be done soon. the researches on influence of various policy actors including less important policy actors should be the next research issues. With this paper, the author is somewhat satisfied that it is just starting in this research area. However, this research is not that satisfactory because of lacking previous studies. The author is expecting further researches on these fields. It promises desirable future of local autonomy.