Abstract: This essay links the constructivism theory of Rawls in the early and late period, namely his Kantian constructivism and political constructivism. By procedurally demonstrating practical reason’s ability to construct and justify moral principles, Rawlsian constructivism successfully vindicates a Kantian conception of practical reason without resorting to controversial metaphysical presuppositions. It also provides a rational framework for reflection and dialogue that achieves moral agreement, or reduces destructive moral disagreements. Rawls’ constructivism is a theory that seeks a moral solution on the basis of recognizing the fact of moral disagreement. On the one hand, this theory insists on the practicality of reason, and on the other hand, it shows a moderate openness.