Based on the documents kept at the National Archives Center II, the author reviews diplomatic activities of the government of the Republic of Vietnam in the struggle against China's invasive plots and actions over Paracellslands of Vietnam. Those activities included:the provision of documents, evidence and analysis of geography, history, administration, the process of establishing and implementing continuous sovereignty of Vietnam over Paracellslands in centuries from different angles for the press in the country and abroad. In particular, the government of the Republic of Vietnam took advantage of international forums to protect its sovereignty over Paracel Islands, issued bilingual "White Paper", issued a proclamation confirming Vietnam's sovereignty over the Paracels as prescribed by international public law. The government of the Republic of Vietnam carried out those activities persistently and constantly so that domestic and international public opinion understood and supported the standpoint of Vietnam. That is the legal and historical basis for the current struggle to protect the sovereignty of Vietnam over Paracellslands.