Abstract: Marx' s theory is a scientific and open theory of social development, not a pure speculative Utopian imagination. Marx' s theory does have a dimension of ideal Utopia about social development, namely, the critical dimension of negating or transcending the then reality. Without it, Marx' s ultimate ideal of liberation of mankind and his ultimate concern on the future of history could not be presented. So advocates, who assert that history has terminated, rebuke Marx' s theory as fancy and impractical one. They are satisfied with unilateral society and can not see mankind' s wide space of possibilities of history, because they completely abandon this dimension of Utopian social ideal.