Kant establishes knowledge and phenomenal world with transcendentalism,while Heidegger holds that the epistemological cognition presupposes the ontological,and the letter is prior. Kant distinguishes phenomena from noumena for moral metaphysics,but in Heidegger's opinion,Kant's noumena are beings instead of being. Heidegger quests for being all his life and insits that thinking belong to being and stresses that representation is identified with being. For Kant the question is how possible synthetical judgments are prior,but for Heidegger the question is how it stands with being. Kant proclaims synthesis while Heidegger suggests answer. Their difference reflects that of time.