Article 9 of the Civil Code, as a provision of green principles, is the source of private law for citizens to fulfill their duty of carbon reduction in civil activities. Moralism and utilitarianism provide legal support for citi? zens’carbon reduction obligations as a legal obligation. The dogmatics of law can explain the new connotation of Article 9 of the Civil Code as the private law source of citizen’s carbon reduction duty in the background of “double carbon”era. Through the systematization effect of Article 9 of the Civil Code in the civil legal system, citizens’duty of carbon reduction can be extended to the field of real right, contract and tort through the infiltra? tion of the green principle, so that citizens as a result of the guidance of the law, the role of self-conscious carbon reduction, and then help to“double carbon”goal.