It is generally held that the ideas Saichō and Kōjō 光定 (779–858) had with regard to the precepts were influenced by Mingkuang 明曠 (late 8th c.). But some scholars point out the differences between Saichō and Kōjō especially with regard to isshinkai 一心戒.One approach to understand Mingkuang’s influence would be to study the quotations from his Tiantai pusajie shu cited in Saichō’s Kenkairon 顕戒論.Therefore, here I focus on the quotations of Mingkuang’s text in the Kenkairon and in Kōjō’s Denjutsu isshinkaimon 伝述一心戒文.Since some quotations from Mingkuang’s text in the Kenkairon are slightly different from the original intention, there is some question whether Saichō placed a particular focus on Mingkuang’s text. However, it is noteworthy that Saichō used Mingkunag’s text to prove the validity of the Mahāyāna precepts as a condition for ordination. On the other hand, Kōjō’s Denjutsu isshinkaimon cites Mingkuang’s text at length, and he accepts Mingkuang’s concept about the heart and precepts as the basis of isshinkai. Some scholars think that Mingkuang’s influence on Kōjō shows his influence on Saichō as well, but we must consider the two cases separately.