Abstract:The absence of an explicit definition of “high seas” in UNCLOS results in the divergence on the “high seas” concept. The United States view is that all part of sea outside territorial sea is high seas and that high seas include exclusive economic zones. China intends to define the “high seas” as an area of sea not including exclusive economic zones. However, this intention is not firmly supported by the treaties and customary international law. China should define “high seas” in its domestic laws and bilateral treaties in order to strengthen the state practices and opinio juris on that intention.