After the U.S subprime crisis has sent a shock wave to global financial marker, enormous government debt problem in peripheral countries is exposed in the crisis. Meanwhile, the top three rating agencies successively downgraded the sovereign credits of Greece and Ireland. Soon after that, the crisis rapidly spread throughout the European Union, the deepening of the European sovereign debt has shown a week link of single currency union. As the highest-level monetary union in the world, euro failed to go against the shock of outside risks, actually, it has deepened the crisis to spread. This thesis aims to study the impact of the current crisis on the European integration or predict the fall of European Union. Considering the crisis is a latest issue remained lasting, this thesis will mainly employ empirical works base on general survey to give an overview of the experiences of crisis. Since the wide range of crisis cannot be imputed to any single cause, complex causes in three perspectives including national level, regional level, and international level see their roles that trigged, exposed and deepened the whole crisis. Furthermore, case study on Greece and Ireland are employed to give an inside look of how nations react after the bailout measure. The debate about bailout measures sees great vulnerability of EU solidarity and necessity of political union. The crisis could be a great opportunity to push forward the further integration of EU. Key words: European sovereign crisis, monetary policy, euro, optimal currency area, European integration