Abstract: In recent years, research on the doctrine of daotong, that is, the "transmission of Confucian orthodox teachings", has been quite fruitful. The new discovery of a document by Charles Hartman, an American scholar, provides important clues and proofs for the generation and development of the doctrine of daotong in the Song Dynasty on the one hand and the deep cultural and political implication in ZHU Xi's doctrine of daotong. One of the important aspects of daotong is the transmission of Confucian culture, thought and theories. It is generally believed that Mencius was the first person who clearly delineated Confucian daotong, HAN Yu then gave it a clear definition, and ZHU Xi completed it. Promoting the status of Confucius above Yao and Shun, and deliberately distinguishing dao from situational potentiality, ZHU Xi's doctrine of daotong demonstrated that the subjectivity consciousness of the intellectuals in the Song Dynasty became mature from awakening. The CHENG brothers occupy a very important position in ZHU Xi's doctrine of daotong. For ZHU Xi, the CHENG brothers were the direct inheritors of Confucian daotong, thus establishing the authentic and dominant position of the learning of Dao(Neo-Confucianism) in the whole lineage of Confucian daotong. From then on, the dispute about daotong was solved. Correspondingly, Neo-Confucians also obtained the power of discourse in daotong and even the whole Confucianism. ZHU Xi affirmed that he was the successor to the CHENG brothers. In this way, he completed the whole lineage of daotong in the Song Dynasty. Thus, defending the purity and authority of Confucian daotong became his inescapable mission in ZHU Xi's whole life.

Key words: the CHENG brothers, ZHU Xi, doctrine of the “transmission of Confucian orthodox teachings”, lineage