Immigration has become a common phenomenon of the national and regional population flow, the EU is no exception. Immigration issues gave rise to a great disaster for the EU and its member states in the field of in social and political areas. Therefore, EU began to consciously and gradually form a common immigration policy. However, because of the impact of EU internal decision-making mechanism and the different governance mechanism between member states, the harmonization of EU immigration policy faces many challenges. This thesis researches harmonization but integration of EU’s common immigration policy by using the theory of Liberal Intergovernmentalism. It can be analyzed in two levels: (1) The formation of domestic preference; (2) EU intergovernmental bargaining. The first chapter introduces the background, objectives and significance of this topic. The second chapter generalizes the current condition of research in three perspectives: public management, politics and economics. The third chapter introduces the theoretical approaches and research methods of this thesis. The forth chapter researches the EU’s immigration policy from the vision of history. According to the theoretical model of Liberal Intergovernmentalism, British and German national immigration policies will be taken as example to be analyzed in chapter five and six in order to show the formation process of domestic preference in the two countries, and explain how they negotiate with other EU member states. The study continues in the last chapter with makes comparison between the two countries and comes to the conclusion, although the EU’s common immigration policy faces many challenges, it will develop slowly and realizes further harmonization. Keywords: European Union, harmonization of common immigration policy, Liberal Intergovernmentalism