Abstract: Marx regards morality as an ideology derived from social life, rather than Kant's moral philosophy of the universal truth beyond history and class. On the basis of social practice, the practice under Kant's transcendental pure rationality is pulled back to reality, and the moral principle is ascribe to the moral axioms which are constantly discovered and developed in line with human interests. In the end, through the establishment of the communist society in the real proletarian revolution, the "supreme good" of the ultimate state of human beings is realized by means of "non-morality", which surpasses the "ideal" world framed by Kant's "rationality". Marx's development of Kant's moral and ethical thoughts is of great significance for us to face the modern moral ethics and solve the modern moral crisis.