Abstract: The unity of legal order means that all current departmental laws and regulations should maintain coordination and consistency, requiring that acts deemed lawful under one departmental law should not be evaluated as illegal under another departmental law. This is an important principle that must be implemented in the process of modernizing the rule of law in China. However, due to the differences in the regulatoryscopes and tasks of various departmental laws, the unity of legal order has not been fully realized. By analyzing the unified theory of legal order and the theory of illegality relations, a moderated theory of relative illegality should be recognized for the judgment of criminal illegality. Although criminal law serves as a post-law to civil law, administrative law, and other legal norms, the posterior character of criminal law does not imply that the judgment of criminal illegality is subordinate to the illegality judgment under the antecedent laws. The judgment of criminal illegality from the perspective of the unified legal order should possess relative independence. The judgment is based on the overall independence of the tripartite crime theory system. A conduct possesses criminal illegality when it satisfies both the constitutive elements and the element of illegality, rather than being merelyevaluated under the antecedent laws. The independence of the judgment of criminal illegality is relative; legality under the antecedent laws constitutes a ground for excluding criminal illegality. This is specifically embodied in the function and value of "decriminalizing", which operates at the level of either constitutive elements conformity or illegality.