The, Guardian Council in his procedure, has sometimes paid attention to moral values and Islamic criteria to examine the conformity of the approvals with constitution and Islamic criterion. Should the Guardian Council be sensitive to the moral provisions of the constitution or the moral precepts that have a firm religious basis. This study intends to show how the Guardian Council safeguards the ethical principles of the constitution and Islamic criteria. This study will be done through descriptive- analytical method and study of constitution, the opinions of the Guardian Council and legal books and documents. The research findings indicate that although guarantee of the moral principles is not explicitly predicted in the Constitution for the Council, its critical role in safeguarding the ethical values within the task recognized by the Constitution cannot be denied. Although the functioning of the Guardian Council in this regard is criticized in some cases; this body is the protector of rule of law as the guarantee of moral values and proper functioning of the pubic power in this regard. In addition, it plays the key role in preserving the morality and ethic. This is fulfilled through conforming the approvals of the parliament with religion and constitution, commenting on the public regulations and interpretation of the principles of constitution.