Foucault’s study turns to the problem of subject in 80’s, and he uses the historical material of Greek and Roman periods. This thesis discusses the reason why Foucault studies the Ancient period, and it also point out a framework of historical ontology in the late Foucault, which focuses on subject and uses the technologies of the self to be the practice of subjectivation. Moreover, the issues of ethics and truth are also related to the subject. If we use this framework to interpret the Greek and Roman periods, by describing the features of the history, we can discover that it is an important period of the transformation of the view of subject, ethics and truth. Through the historical research, Foucault demonstrates a new dimension of ethics and epistemology.