The main purpose of this study is to find what steps are needed for a system for CO2 emissions trading to be formulated as government policy, using System Thinking approach. First, this paper analyzed Korean newspapers to consider the social issue regarding CO2 emissions trading. There were more articles related to international issues than domestic ones before 2008. This trend, however, became reversed from January 2008, which means that consideration of CO2 emissions trading has been discussed as a domestic social issue from 2008. Second, it analyzed speeches by former president Roh Moo-Hyun and current president Lee Myung-bak. In particularly, President Lee Myung-bak declared "Low Carbon and Green Growth" as a new growth engine and a Korea's vision of the future national development. Third, it examined which government agencies, including departments and committees, are pursuing policies regarding climate change, global warming, and CO2 emissions trading. Most policy has originated in the Ministry of Environment, although policy alternatives have been proposed in other agencies including the Ministry of Knowledge Economy. The study concludes that the political consideration has played a major role in the policy agenda-setting process of the CO2 emissions trading in Korea.