The Buddhism exchanges between China and Korea during the Mongol-Yuan period had reached a peak in Chinese history. Many Korean Buddhist monks came to China at that time. Yi-Xuan（義璇）was one of them. An important person in the history of the Yuan-Korean Buddhism, he was nominated by the Mongol Emperor as the abbot of the Great Tian-Yuan-Yan-Sheng Temple（大天源延聖寺）, one of the imperial temples in the capital area. He had once returned by imperial order to Korea for praying for the Emperor and the state. This paper aims at giving an overall look upon Yi-Xuan’s life, including his family lineage, his religious belief, his important deeds, and his friends and disciples. It will also explore the significance of assignment to imperial temple’s abbot in the Yuan dynasty, and explain the development of the Tiantai Sect（天臺宗）in Korea.
