The relation between nature and grace is an important subject in Christian theology and some other important subjects are based on it. This subject was controversial among Catholic Church and nouvelle theologie in the middle of previous century. German Catholic existential-transcendental theologian, Karl Rahner, was in some agreement and disagreement with both of them. He expressed his theory in this context and by use of some concepts such as supernatural existential, uncreated grace, and obediential potency, attempted to make an improved statement of the subject. Grace in the theology of Rahner is as important as it is called Theology of Grace. His theory contains important connotations for both catholic theology and his theology, and has been dealt with some criticism that will be examined here.