Since European Coal and Steel Community was established in April 1951, EU has enlarged for five times. The membership has increased to 27 states from the initial 6 founding members. We may well say that this is a great initiative and achievement in human history. Especially the fifth enlargement consists of 2 Mediterranean countries and 10 countries in central and eastern Europe. The number of new members is more than the amount of the past four expansions, and its meaning and effect has attracted the attention from all around the world. The fact of the joining of several central and east Europe countries has three implications. First, ruling by the Communist Party, these countries were equal to the Soviet vassals which obstructed the normal development of these countries, not to mention of the threat to their independence and autonomy. These countries' integration into EU could be tantamount to the termination of sovietization. Second, following the collapse of Warsaw Pact, the USSR crumbled. In order to fill the vacuum of security in east Europe, these countries joined NATO and EU for reason of their own security and getting closer with the Western. Third, the pursuit and insistence of freedom, democracy, human rights and market economy is regarded as universal values to which all democracies commit. Only the integration into NATO and EU by the central and east European countries can strengthen their national interest. Furthermore, we can discuss its economic meanings. First, when the central and east European countries are proceeding their economic reform, they need the western countries’ assistance in form of finance, technology and business administration. As a result, with the mighty economic power of EU, these former socialist countries can get financial and technological aid more easily. Second, EU has established a prosperous market, which is really a support of the central and east Europe countries for expanding overseas market. Third, with the integration in EU and NATO, the central and east Europe countries can access to the resources of EU and the other developed countries. Finally, these are still noticeable effects of these central and east Europe countries' affiliation with EU. How the EU constitution is formulated? How to reconcile the estrangement and different opinions between the new and the old members? To what extent is the scope of the interference from the U.S.? Can EU be seen unified and cooperative in its common foreign and security policy? All these above questions can be looked upon as important indications as we observe the further development of EU.