The objective of this thesis is to analyze the reasons of the changes in the British attitude to the EEC. Drawing on the history of UK-EEC from 1950 to 1993 to explain what prompted Britain from opposition to willing to join the EEC. All changes are mainly derived from the British national interest demands, including sovereignty, economic interests, political demand and other factors. In addition Britain's attitude to the EEC is also affected by the changes of international environment and the behavior of the leaders. Key Words: the relationship between the UK and the EEC, national interests, policy, leaders' behavior