We often think Frankfurt School’s theory of art is romantic. “Aesthetic Utopia” has almost become the synonym for art theory of Frankfurt School when we talk of it. But this accepted evaluation is still open to discussion through reexamining the appraisal of “Aesthetic Utopia”， and especially indicating the ontological basement of the general conviction on which the appraisal is established. This opinion relates to the Metaphysics’ rule to our life. By this means we can further clarify and recognize the basic nature of Frankfurt School’s theory of art.