This report reviewed the China’s jurisdiction in the South China Sea and regional interactions since ancient times. It testifies to the basis on which China claims its historical rights in the South China Sea, given that international law is the prerequisite for historical rights. In the meantime, the study also argues for the international legal basis of the dotted-line in South China Sea by analyzing historical documents since the 20th century, including official communiques, maps, historical monographs and more. The historical and legal analysis thus puts forward recommendations to the Chinese government on properly dealing with the dotted-line and historical rights.