By analyzing 844 questionnaires on public opinion of the South China Sea territorial conflict, This paper believes that domestic public opinion of the South China Sea territorial conflict has the differences of strong group polarization and weak group polarization. Public opinion on the South China Sea has the characteristics of self-contradiction and irrational part. In an era of new media, public opinion has a “dike” effect on the decision making of the South China Sea. If public opinion wants to affect foreign policy decision making, it needs to do it by the way of network and media. The public believe that individual almost cannot directly affect decision making of the South China Sea, but he can affect the latter to some extent by media. The characteristics of group polarization, self-contraction and irrational part of public opinion put great pressure on the decision making of the South China Sea. The government should consider how to better manage public opinion, allay nationalism, thus keeping a good homeostasis between public opinion and decision making of the South China Sea.