T'ai tsung (太宗), the Second Emperor of the Ming (明), made his way to the throne by disloyal means, i.e. the Ching-nan (靖難) Rebellion. And the ringleader of this rebellion is asserted to be the Buddhist monk, Tao-yen, 1335-1418. Afterwards he was "graciously permitted" to return to secular life by the supreme commond of the emperor and then given the name of Yao Kuang-hsiao. But it is said he still continued to live the rigorous religious life. The author deals in this article with his activities as a monk, his works on Buddhism, especially on the doctrine of the Ching-t'u (淨土) sect, and his "Tao-yu-lu" (道餘錄) written against Confucian attacks on Buddhism. Finally, the author tries to make cIear his part in Buddhist affairs under the earIy Ming dynasty.