Abstract: Since the end of the Iraq war, Iran's nuclear problem has become anoth er hot issueof the Middle East that the international community is concerned wit h. As an major entity with political and economic interests in the Middle East, European Union began to get more actively involved in Iran nuclear problem than at any time since World War II. It not only acts against U.S, but also has bee n negotiating with Iran patiently for many years. This move is just a reflection of the shift in European Union's diplomatic strategy in the issues of the Middl e East in the postcold war era.