一九四九年，中共在北京建立政權，宣稱在國際社會代表全中國，開啟與中華民國政府數十年的中國代表權爭奪戰。本文大量引用原始文獻，以萬國郵政聯盟為例，呈現中華民國政府捍衛代表權策略的轉折。中華民國政府起初過於大意，郵盟代表權為中共奪取，經外交折衝後回復。但是美國阻止中華民國政府進一步的積極鞏固策略，一同聯合國席次保衛戰，改採消極的拖延策略，並將爭議集中於聯合國處理。一九七一年，中共取代中華民國政府的聯合國席次，郵盟在內的眾多國際組織遵循聯合國決議，中華民國政府被迫撤離，臺灣郵政總局必須以非郵盟會員身分的權宜性手段維持國際郵遞。

The question of representation of China in international organisations had been discussed since the Communists won against the Nationalists in 1949. The Nationalist Government did not vanish, as they fled to Taiwan and the question therefore became more complicated. For a long time, the United States, for strategic purposes, supported Taiwan in its claim to represent China in the United Nations and other relevant organisations, including the Universal Postal Union. On the other hand, the Soviet Union and the other communist countries supported the Chinese communists in their application for membership and to replace Taiwan as the representative for China's membership. In the case of the Universal Postal Union, this essay would discuss both the communists' tricks and the strategies set by the Nationalist Government in defence of the China membership they had represented. This essay would also reveal the Nationalist Government's response to the international postal policy when Taiwan lost its membership of the Universal Postal Union in 1972, after the failure to defend its membership to the United Nations in 1971. The case of the disputes in the Universal Postal Union might be seen as a focal point of the dilemma faced by Taiwan in international organisations from 1949.