There are two ways of understanding justice in the Ｒepublic: ①Understanding justice from a personal perspective; ②Understanding justice from the perspectives of the polis as a whole，the soul as a whole and their rela-tionship． Through Socrates’refutation of the way to understand justice from an individual perspective in the Ｒepublic，it is shown that neither wealth nor the interests of power can give a reasonable explanation of justice． It is proper to comprehend justice by considering the whole city-state，the whole human soul and their relationship as a whole． Because it involves the city-state，soul and virtues which are closely related to the “good life”of human beings． This is Plato’s thought of justice about how people should live their lives．