The Nuremberg and Tokyo trials for the first time in human history，established the criminal nature of the war of aggression by resorting to international criminal justice，prosecuted and demonstrated the individual criminal responsibility of the accused against crimes of peace，war crimes and crimes against humanity，shaped the geopolitical pattern after the war and laid an international peace order including East Asia.However，due to the difficulty in seeking the basis of the empirical law，the moral direction is in the same angle as the winner's direction，and the prevalence of the weak international rule of law and the power center theory in international relations，the post-war trial has been constantly subjected to the violation of the principle of legality of crimes and punishment，which is the accusation of “victors' justice”.How to understand the conclusion that originated from the Nuremberg judgment，which was subsequently invoked by the Tokyo Trial“no law does not expressly provided for the crime”，related to how to historically treat the principle of legality of crimes，how to grasp the relationship between morality and law，and how to understand the role of international judicial decisions in the formation of the international order.Only by answering these three questions well from the perspective of history and based on normative analysis can we see the value and normative role of post-war justice and international criminal justice，properly evaluate the basis and function of post-war justice，and provide a new dimension for thinking about the role of international criminal justice in maintaining international peace and security.