The issue of South China Sea is one of the hottest international disputes in South East Asia due its location amid the connection between Southeast Asia to Northeast Asia and the rich resources. The undecided maritime delimitation makes the situation more complicated. Because each one of the ASEAN Claims has her own consideration of the interest, their claims and policies confront from each other's, and no consensus has been reached. However, encountering the fact that China proclaimed the entire region of South China Sea, ASEAN Claims attempt to unit themselves to deal with the threat, to negotiate the issue of South China Sea with China as a whole, and attempt to internationalize the issue. Thus, this paper is aimed to realize under what circumstance, ASEAN Claims will tend to unite in the issue of South China Sea, or vise versa, in what circumstance makes ASEAN Claims tend to collapse. According to the "Balance of Threat," China's threat to South China Sea affairs leads the changing of the unity of ASEAN Claims directly, and influences the consistency of South China Sea's policy. Besides the United States, the other side of the balance of the two counter powers, the treat brought by China in South China Sea affairs is the key to influence the South China Sea policy consistency of ASEAN Claims. "South China Sea Core interest" is one of match instance.