The issue of security among ASEAN countries has always been an interesting phenomenon with many aspects characterized by the complex interdependence between domestic and foreign affairs. In particular, increasing disagreements over the Spratly Islands in the South China Sea region involving ASEAN member countries such as Brunei Darussalam, Malaysia, the Philippines, Vietnam disputes arising from the South China Sea conflict have sparked bilateral conflicts and inter-state disputes have raised fears of possible outbreaks of military conflicts with China. This is what prompted ASEAN countries to include regional security issues into the official agenda of ASEAN. This study aims to describe, explain and analyze the role of ASEAN Cooperation in reducing South China Sea conflict. Indonesia is trying to prevent haze from creating conflict between Indonesia and Malaysia through discussion and negotiation. The role of ASEAN in reducing the conflict is analyzed by using qualitative approach. In this study, the theory used is conflict transformation approach. The role of ASEAN effort in reducing South China Sea conflict is by changing the bilateral relation by China which China only wanted to do the settlement or cooperation just with the conflicted countries and by its preventive diplomacy is a success. Some of the conflicted countries in ASEAN are now in cooperation and do some agreements with China to strengthen and bound the relation between countries. And make better development in many aspects of governement both for ASEAN countries and China.