The unilateral imposition of carbon border adjustment tax by the European Union under the Paris Agreement violates the principle of common but differentiated responsibility. Building a quantitative trade model based on the global value chain can simulate and evaluate the emission reduction effects and trade welfare impacts of carbon border adjustment taxes under the Paris Agreement. Research has found that： Unilateral taxation by the European Union and taxation based on carbon price differences among countries can alleviate carbon leakage to varying degrees， and will be beneficial for the welfare improvement of the European Union and Japan； Using member states to tax non member states has a higher emission reduction efficiency compared to mutual taxation among countries， and is more conducive to the welfare level of the United States and developing countries such as China， India， and Russia compared to the first two taxation methods. The withdrawal of the United States from the Paris Agreement has significantly increased the carbon emissions of non member countries and member countries， leading to more serious carbon leakage problems. The imposition of a carbon border adjustment tax will significantly reduce the welfare level of the United States. If China withdraws from the Paris Agreement， it will also exacerbate global carbon leakage. Implementing a carbon border adjustment tax can reduce carbon leakage and encourage China to reduce emissions through structural effects， but it will significantly worsen China's trade conditions and lead to welfare losses. Further analysis of the global value chain mechanism indicates that the close connection of the global value chain will significantly reduce the intensity of global carbon emissions and total global emissions.