In the middle to late 19th century, the traditional tributary system centered around China began to show signs of instability due to external pressures, and the suzerain vassal relationship between China and Korea also entered a crucial transitional period. Prior to 1879, the Zongli Yamen always consistently maintained in its correspondence with foreign countries that the suzerain-vassal relations between Modern China and Korea was “vassal but autonomous” relationship. However, this concept of “vassal autonomous” began to change after Japan annexed Ryukyu in 1879. Officials of the late Qing Dynasty represented by He Ruzhang, engaged in multiple discussions about the East Asian situation and the suzerain-vassal relationship between Qing and Korea, and gave birth to the argument that “vassal≠autonomy”, and their positioning of the Korea began to take on the color of Elements International Law. Subsequently, the Qing government’s policy towards Korea gradually shifted from the traditional suzerain-vassal relationship to the modern treaty system, and public law in the “vassal state” is increasingly strong.