Compared with other basic principles of civil law (equality,voluntariness,fairness and integrity),the principle of public order and good custom has the uniqueness of value and the highest status. The uniqueness of its value lies in the dual legal nature of "value declaration" and "referee's standard",and its status is highest in that it carries the most fundamental value goal of civil law. The fact that the principle of public order and good custom has the factual face,the reducibility of the fact,and the open requirement of legislative technology gives the reasons for its dual legal nature. When the principle is applied as legal norm,it needs to be interpreted in a creative way,to meet the degree of certainty requirement of legal rules,and to eliminate possible differences. Therefore,it is necessary to enforce the requirements of "no escape to general provisions" and "modesty",in order to prevent the chaos appearing in the application of the principle of public order and good custom.