As one of the most integrated organization, European Union has played a leading role in environmental protection, and it also has a vital position in the international environmental affairs. Environmental protection is an important part of the Union's policy, and in this area, European Union is shared competence with its Member States. Although the initial concern of the European Community on environmental issues stems from issues such as trade in the Community, with the strengthening of public awareness of environmental protection and measures taken by other countries for environmental protection have been effective, the importance of environmental protection in the Community's agenda has been gradually enhanced. The European Community not only gradually promoted the status of environmental protection matters in treaties, but also paid more attention to the implementation of environmental laws and policies, and formed a comprehensive implementation system based on the market incentives. Today, environmental protection has become a vital part of EU external policy and international cooperation. Generally speaking EU environmental legislation is positive, timely and advanced, it not only concerned with legislation, but also concerned about the implementation of environmental law. The Union's regulations on environmental protection have gone a process from simple to concrete. Meanwhile, it also focuses on dealing with Union's internal and international environmental problems. The Single European Act provides a specific legal basis for environmental protection. Treaty on European Union formally formed the concept of sustainable development. The Amsterdam Treaty makes the sustainable development as a priority for the Union. The Lisbon Treaty reaffirms that the Union is committed to solving global and regional environmental problems. Broadly speaking European Union's environmental law includes pollution control, natural resource protection, waste management, combating climate change, etc. First of all, this thesis pays attention to the evolution of Union's environmental law and policy, including seven Environmental Action Programs and the emergence and development of provisions with regard to environmental protection in Union's Treaties. In order to better understand the EU environmental law and policy, the content including objectives and principles could not be ignored, Based on knowing the basic contents of environmental law and policy of the European Union, the thesis examines the implementation of Union's environmental law and policy and analyzes how to ensure the implementation, enforcement and compliance; Furthermore, from the institutional perspective, this thesis examines the impact of Union's enlargement on environmental policy implementation as well. As more and more environmental issues arise, environmental litigations are increasing, In this regard, it is necessary to know the environmental liability system and the plaintiff qualifications in environmental public interest litigations. Finally, this thesis examines the current situation of Union's environmental law and policy and put forward the future challenges as well. In order to address these complex challenges, the thesis presents countermeasures to solve these issues and to ensure that our environment could be protected better.