Abstract: Cooling-off period is applied to divorce cases in many countries. In China， cooling-off periods applies only to divorce by agreement， but has been the focus of controversies since it came into effect. Supporters hold that the cooling-off period prevents couples from making impulsive divorce decisions， but others say it sets up procedural obstacles and interferes with private freedom. Restriction of the basic rights of common citizens by public power must comply with the principle of proportionality， the basis of which is human right protection and includes three aspects: appropriateness， necessity and balance. Seen from the perspective of the principle of proportionality， the constitutionality of the cooling-off period system is legitimate in legislative purposes and meets the requirements of appropriateness and necessity. But affecting the interests of the vast majority for the interests of a minority is not in line with the principle of balance and the basis of constitutionality is slightly lacking. It is urgent to perfect the cooling-off period system， making it conform to the purpose of the constitution and maintaining the authority of the constitution.

Key words: cooling-off period before divorce, freedom of divorce, the principle of proportionality, legitimacy, appropriateness, necessity