Abstract: Transcendental logic is the main part of Kant's epistemology, which has both transcendental structure and logical structure. It also includes the "logic of truth" and the "logic of illusion". Transcendental logic has a symmetric structure. Among them, the square of opposition, propositional logic and syllogism, which is correspond to the conceptual analysis, principle analysis and illusion analysis. In the philosophical dimension, transcendental logic is the unity of epistemology and logic. Among them, logical clues constitute the "navigation" of Kant's epistemological maze. Logic is also the "scaffold" of the epistemological system. In the history of logic, transcendental logic pays attention to form and content, which means the rudiment of non-classical logic, promotes the development of modern logic philosophy, and it also inspired Hegel's dialectical logic.