Abstract: According to the general theory of the criminal law, clarity is one of the standards of legitimacy. But from the standpoint of the three-dimensional criminal law, the construction of this principle needs to go beyond the criminal law theory system and combine the whole legal system to make a comprehensive construction. From the perspective of the constitutional control, this principle is an important standard of constitutionality of the criminal law. The principle has its own theoretical and institutional background in different legal systems. But as legal methods, this legal principle is also an important technology which can provide reference for the construction of Chinese legal theory.