The interest of the child means managing his affairs in such a way as to ensure the accuracy of his physical development and his moral and intellectual civility. The interest of the child arises of the particular physical and psychological state of the child because the child is not an evolved person but is on the path to becoming an adult and wise person. Therefore, the interest of the child is different from the interest of the adult man. For this reason, in conflict between preserving the child's psyche and preserving his property priority is by preserving his soul and intellect. Iran law and the United Nations Convention on the Rights of the Child have accepted this criterion. Because of the joinder of Iran to the Convention on the Rights of the Child, the Convention, based on Article 9 of the Civil Code, is governed by the domestic law of Iran, and it can be inferred from the interpretation of the existing laws and the completion of the reticence of the law, such as the time when the child withdraws from custody, to the present Convention, In this direction, it has been cited in some of the rulings issued to this Convention as one of the directions of the ruling.