After the 9/11 attacks in the USA, terrorism has become the focus of the whole worlds and the international hot spots in great power relations. The EU, as the hardest-hit of terrorism, its counter-terrorism policy moves in zigzags, and has twists and turns. 9/11 attacks, as a historic terrorismnode, have great significance, and as the same, the EU's counter-terrorism policy is divided into two periods by 9/11 attacks. Before 9/11 attacks, the root causes of terrorism in Europe mainly are anarchism, ethnic conflicts and ideological conflicts. After 9/11, the main terrorist threat to the EU mostly focuses on ethnic conflict, and types of terrorism also have new changes, the situation of terrorism in EU is still grim. The EU's counter-terrorism policy, not only has made a positive contribution to Europe and the world's fighting against terrorism,promotesits own integration and further enriches and improves the international anti-terrorism theory, but also conduces to the formation of international multi-polarity. EU counter-terrorism policy has made great achievements inroots prevention, security protection, police and judicial cooperation, international cooperation. However EU counter-terrorism still faces many challenges in the consensus reaching, information exchange, foreign economic sanctions, and authority of the EU its own, which requires the EU to make further efforts. Although European and American establish a cooperative structure of the system in intelligence, finance, customs, aviation and port security, bio-defense 7 and critical infrastructure protection and other fields to enhance the cooperation between them, but because of the way to eliminate the threat of terrorism still exits great differences, the EU-USA counter-terrorism cooperation also has a long way to go.