After entry into force of the Paris Agreement, the EU, the United States and other countries may adopt the unilateral carbon border adjustment measures to strengthen the effect of reducing emissions and harmonize the environment. And climate trade barriers will become the new foc us of international trade law. However, there is still controversy over legitimacy of carbon tariff under the framework of International Trade Law. The future design of carbon tariff legal system will turn from“process tax”to“product tax”comply with the WTO rules, following good-faith effort in negotiation, fair and due process, flexible design principles, which may comply with GATT Article 20 environment exception. To this end, China should adhere to the principle of distinction, and actively promote the multilateral carbon emission reduction mechanism, to resist unilateralism, and make rational use of WTO rules to resolve disputes.