Abstract: The suzerain-vassal relation between China and Vietnam lasted from 1667 to 1885. During the 200 years, as a tributary state of China, Vietnam formally respected China as a superior sovereign．But in reality, it adopted a diplomatic policy of“inside as a monarch and outside as a vassal.” This policy was designed to gain more national interest and to win a more“equal”status with China. Hence, every time when Vietnam paid tribute to China, the Vietnam court always fully prepared for the mission, especially the envoys. Those envoys fully understood Confucian Teachings. As diplomatic specialists，they cautiously behaved in order to maintain good relations with the Heavenly Dynasty. However, they also racked their brains to place Vietnam under an equal position with China. They played an important role in keeping a stable relation between the two countries．