This paper tries to show how Augustine criticizes the Academic Skepticism in the Contra Academicos, and how he understands the tradition of Platonism. Looking generally at several views of the Academic Skepticism and analyzing the arguments of the Contra Academicos, we can get the following conclusions: 1) Augustine tries primarily to refute the arguments of Carneades. There have been controversies about whether the arguments of Carneades are totally ad hominem arguments against the Dogmatics (view of Cleitomachus) or those arguments are Skeptic's own (view of Metrodorus). But Augustine contends that the Skeptic arguments(especially akatalepsia and epoche) force young men to give up searching for the truth and will be stumbling blocks to the acquisition of happiness. 2) According to Augustine, nevertheless, the Skeptics don't believe themselves the akatalepsia of things. So the Skeptic arguments are means to test the ability of pupils, while the Academic Skeptics concealed Plato's real view which was guarded as "mysteries" and buried it as a golden treasure to be found someday by posterity. That is, as Philo of Larissa maintains, there is no difference between the old Academy and the new Academy. And Plato's mysteries can be taught only by the method of concealment. 3) Therefore, although Augustine criticizes the Academic Skepticism in the Contra Academicos, his real purpose is not to refute the Skepticism completely, but to explain the hidden aim of the Skeptic arguments and to warn of misuse of these. There remains a question about the validity of Augustine's view of the tradition of platonism and the teaching of concealment. In the view of Augustine, however, the Skepticism was not only a barrier to remove for the acquisition of happiness, but also something to embrace for the harmony between faith and reason.