With the change in business environment of banking industry and regulatory environment in recent years, the fragmented banking market gradually emerges. Under the background of economic downturn, situations of member states’ (MS) banking business in the European Union (EU) banking business are not optimistic. The vicious cycle of sovereign debt crisis and banking crisis forces the European Union to launch a system at supranational level to cope with the crisis. Spread of banking crisis is the result of deepening European-banking integration. However, it creates a good chance to promote integration of banking industry. After the European Banking Union (EBU) putting forward proposals, the legal procedure of its first pillar, the Single Supervisory Mechanism (SSM) enters into force. This pillar is the milestone of future banking union and closely related to revolution of banking supervisory integration, In this thesis, I briefly analyze nature of the EU's banking industry integration, especially supervisory integration in the post-crisis era; review the development of the EU banking integration before the international financial crisis; test integration theories of negotiations about proposals of the European Banking Union and predict future of supervisory integration. I argue that the process of banking integration before global financial crisis has contributed to further integration like the cross-border banking business. Nevertheless, the crisis discloses that banking integration of the EU lacks a strong regional supervision system, which was the main systematic reason for banking crisis in the EU. Therefore, I intend to explore the future developing direction of the EU's supervisory revolution based on theories analysis and empirical analysis. This thesis comprises seven chapters. The first chapter will introduce banking integration and the EBU, which will include the background, the definition, the main content and timeline, the barriers to enforcement of banking integration and the future EBU. Second chapter is the literature review. In the third chapter, I will summarize the development of banking integration in the pre-crisis era. The third chapter is the introduction of theories and methods. The fourth chapter will focus on the improvement and supervision of banking integration after the global financial crisis. Chapter 5 will focus on the introduction to the theories and the methods. In Chapter 6, the analyses will focus on the bargaining of the first pillar, namely Single Supervisory Mechanism, by testing the four theories and finding out the most convincing explanations of the negotiation leading to the deeper banking supervisory integration. The last chapter will provide a conclusion about the testing of various theories of European integration. Keywords European Banking Union; Intra-European diplomacy; the Single supervisory mechanism; European financial crisis; the theories of European integration Research Question What contribution can existing theories of European integration make to explain the negotiating record attending the creation of the Single Supervisory mechanism to anchor a European banking union?