作為一個特殊的國際關係行為者，歐盟的權力角色長期以來在學界備受重視，學者發展出許多不同的概念，來描繪歐盟此不同於傳統國家的國際行為者。然而雖有許多不同的概念描繪歐盟的權力角色，目前卻缺乏一個可普遍適用的分析框架，來觀察國際行為者的權力角色，故本文試圖建立一權力角色分析框架，主張應由「機會」、「工具」及「實踐」三面向，來觀察國際關係行為者的權力角色。在對歐盟不同的描述中，「規範性權力」近期最受關注，因此本文將以權力角色分析框架，來觀察歐盟在國際社會上的規範性權力。在案例選擇上，歐盟在環境議題上引領發展，並以條約將「永續發展」訂為歐盟的重要目標之一，故本文將聚焦在容克執政期間，歐盟在環境議題的作為，觀察歐盟在面臨內外挑戰的時期，其於國際社會上的綠色規範性權力實踐。

As a special international actor, the role of the EU’s power is a hot issue in academic debates. Scholars develop several concepts to describe the EU as an actor which is different from that of traditional national states. Despite various concepts being proposed, there so far has been no analytical framework developed to observe the role of international actors’ power. As a result, this essay tries to develop an analytical framework of the role of power, which observes international actors from the perspectives of opportunities, instruments and practices. Among the various descriptions of the EU, “normative power” is a highly-debated one. This essay uses the analytical framework of the role of power to observe the role of the EU’s normative power in international society. This research chooses to analyze environmental issues, as the EU takes a lead in this area and sets “sustainable development” as an important goal in its treaties. The development of environmental issues in the EU during Jean-Claude Juncker’s Mandate will be observed in this research to discuss the EU’s practice of normative power in international society during this difficult time, in which the EU faced both internal and external challenges.