Abstract: The end of the Cold War and the development of globalization have caused the traditional territory safety to give way to the non-traditional security.Facing transnational crime,immigration,pollution,regional conflicts,drug trafficking,the proliferation of weapons of mass destruction and other non-traditional security threats,the EU,as a political and economic organization and a growing military organization,is more capable of meeting this comprehensive security challenges than NATO.Although there exists the drive of political & economic benefits for EU’s eastward enlargement,Europe can achieve political unification and economic mightiness.The most motive for EU’s eastward enlargement is to achieve Europe’s comprehensive security,including traditional security and soft security.To some degree,the eastward enlargement is an important security strategy for EU.