Abstract: Since its birth, the Enlightenment has revealed to mankind the core of rationality, which is placed in a lofty position. The light of rationality then shines over the whole of Europe. Human beings begin to pursue their own freedom and liberation by breaking through all kinds of cages with their unique rationality. However, in the process of pursuing the supremacy of reason and freedom, Kant put forward the meta-question of what is the enlightenment, which is tantamount to bringing a different landscape to the people who indulge in the cave of reason. Kant clarified the boundaries of human rationality through careful reflection on rationality and criticism of rationality, and pointed out the limitations of human rationality, which can not transcend experience and phenomena to reach the care of the transcendental world. Marx believed that the rational freedom that people have been striving to achieve since the Enlightenment was just conceptual freedom. Kant's criticism of reason did not touch the foundation of real society. Kant only restricted human reason in epistemology. Based on the limitation of human rationality, Marx turned his criticism of rationality to the criticism of the reality of capitalist society, and his practical philosophy changed the paradigm of rational criticism.