Occupy Wall Street is in essence a left-wing social movement against social polarization. There are both structural and mechanismic causes for the movement's rapid surge. The former is primarily the growing gap between the rich and the poor in the developed countries caused both by the changes of domestic and international political pressures and by the deepening of economic globalization. The latter mainly include the space selection of the movement, the overreactions of the government, and the movement's strategy of openness. The principal reason for the timing of its eruption in the latter half of 2011, when the economic and political situations had improved, is that such conditions as social demands, tactical solutions, and organizational preparation were lacking before. Because there are still social needs and policy opportunities for a left-wing movement, it is possible for this movement to overcome serious funding and organizational problems and therefore awake soon. No matter whether or not it recovers, Occupy Wall Street will in a considerable period both force the governments to take more policy considerations in restraining income and wealth inequalities, and enhance political polarization in the United States.