The increasing tendency to peaceful uses of atomic energy alongside the fear of proliferation of nuclear weapons and nuclear war led the international community to conclude the 1968 treaty on non-proliferation of nuclear weapons (NPT). The non-proliferation of nuclear weapons, the right to use peaceful nuclear energy and nuclear disarmament are three main pillars of the treaty. However, the concepts, contents and limits of rights and obligations of state parties to the treaty on the pillars, constantly have been the subject of disagreement among different groups of states, notably among Non-nuclear states and nuclear states. The recent challenge on Iranians nuclear activities including the Iran’s right to enrich uranium is a clear instance of these disagreements. This article described the legal nature, its contents and limits of right to use peaceful nuclear energy as one of the main pillars of NPT and then, analyzed the Iranians right to enrich uranium. The use of nuclear energy is a general and inherent right of all states under general international law. However, this right is limited to the non-proliferation and manufacturing nuclear weapon by NPT.