Born in Sa-cheon Si, Gyung-nam, E-jung(1512-1571) worked during the dynasties of Myung-jong and Sun-jo when Confucianism flourished. E-jung has not been able to receive much attention academically, although he is considered as a scholar who changed Sa-cheon(a sort of dead ground of academics and education) to the core of the Confucian thought. Considering him as a noted disciple of E-whang, one may think the situation sounds rather absurd. Several reasons can be brought about in relation to the phenomenon, but the most important of all may be the disappearance of 70-80% of his works during the Japanese Invasion of Korea in 1592. Most of his remaining works are poetry. Examining thoroughly E-jung's studies and thought in the poetry and his life history written by Jeong-do, this article looks into his life, his studies in adversity, the relation of teacher(E-whang) and disciple, the characteristics of his studies and thought, and his contribution to the history of the Jo-sun Confucianism.