Abstract: The EU directive of including aviation activities in the scheme for greenhouse gas emission allowance trading has challenged both the operation of international aviation industries and international law,which has been heavily criticized by aviation associations and industries of many non-EU countries,especially those from US,China and India. Airlines of USA initiated a lawsuit in 2009 in UK. Concerned airlines from more than 29 countries,including China and India,challenged and declared the illegality of EU’s measure,while EU insisted the legitimacy of their measures. This article has discussed the EU directive of aviation ETS from the perspective of international law,especially the principle of common but differentiate responsibility and article 2 of the Kyoto Protocol,and reached the conclusion that EU’s unilateral measure is illegal and inappropriate on international level.