Since the return，the Macao Special Administrative Region has been a special political and economic entity in China，It has the universality of general international relations actor，and has foreign affairs rights that the local governments of unitary countries do not have，or the particularity of greater independence in foreign relations than the sub-national governments of federal countries. It has an unique role in the overall diplomatic layout of China. However，in the face of rapid changes in the internal and external environment，how Macau can leverage its system advantages of “one country，two systems” to make new contributions to China’s overall diplomacy has become an important topic in the study of Hong Kong，Macau and international relations. The article first sorts out the theoretical application of subnational government diplomacy and Macao’s foreign relations and analyzes the unique role of Macao in China’s overall diplomacy. Finally，by reviewing Macao’s achievements in foreign relations over the past two decades after its return，it analyzes the problems and countermeasures in its practice of foreign relations，so as to improve Macao’s foreign relations mechanism and better serve China’s foreign strategy.