The concept of “social justice” has entered the horizon of Chinese planning academics, and became a hotspot in the discussion of urban affairs, while constantly stimulated by the emerging social conflicts. In fact, the philosophical speculations of justice” and “equity” were nurtured in the whole course of socioeconomic and political theory in Eastern and Western Worlds, leaving rich ideological legacies. Therefore, this paper traces the roots of the social justice discourse back to three major ideological sources: (neo)Liberalism, Communitarianism and (neo)Marxism. It summarizes major social justice ideas in the Western World since the Enlightenment, hence to contextualize thoughts, to distinguish viewpoints, and to uncover origins and successions between theories and theorists. On the one hand, a “distributive justice” that derived from the “moral individualism” and “bottom-line welfare system” advocated by neoliberal scholars has become a “universal value” gradually accepted by the globalized world system (China included). On the other hand, some theories kept trying to redirect the dialogue on social justice from “liberalizing individual freedom” to “establishing the moral standards in collectively living”. The Communitarianism, which rooted in traditional patriostism and the ethics of belief, constantly reminds the individualists that the discussion of social justice should not ignore one’s “communal encumbrance”, “collective responsibilities”, “sense of belonging” and “pride and shame” as a community member. While the theory of “politics of difference”reveals that urban social justice issue involves the “dominative” or “oppressive” power relations between social groups which defined the injustice distribution in the first place. Therefore, hoping for “creating urban commons” and “celebrating city diversification”, a heterogeneous, inclusive and cohesive urban society became the shared vision of a metropolitan living, especially among young generations. From the third source, (neo)Marxists see social injustice as a result of the structural conflicts within the capitalist system. They are using the concept of “the right to the city” as the core analystical tool to explain the “accumulation”, “circulation”, “exploitation”, and “crisis” of capital in the modern urbanization process. The “right to the city” is also serving as the assembly banner for the “new left” in fighting against capitalism in the cities. By reframing the historical and theoretical perspectives on the social justice discourse, this paper is expected to elicit further discussions in regard to the value system, moral standing-point, and professional ethics of urban planners in China.