The aim of the book is to examine the European Union s climate policy in the nexus of domestic policy-making and international negotiations. I firstly test the EU s internal climate policy-making by applying the rational choice institutionalism on the model of institution and preference affect EU s policy outcomes and conclude that: as the EU has a convergent preference, the EU s unique decision-making procedure, the entrepreneurship and EU s membership had been driving EU s climate policies into preferable outcomes. As the EU s preference is divergent, external factors affected the EU s divergent preferences and unified it to approve the ETS in the EU-wide. Second, I examined the relations between the EU s internal climate policy-making and international negotiations by applying the two-level game approach. The findings is that the Kyoto Protocol has a crucial impact on the developments of EU s climate change policies in terms of driving the EU s internal climate policy-making into a regulatory, centralised and market-based instruments direction. In return, EU climate change instruments, such as the EU ETS, are becoming more influential at the international climate negotiations