Ou Yi's Zhouyi Chanjie (An Interpretation of Yijing through Zen Buddhism) is the most complete writing extant on Yijing from a Buddhist viewpoint; therefore, it is an important book for people to study Buddhist Yijing and recently starting to gain high regard in the academic circles. But current studies of the book still mainly focus on such areas as the writing process, contents structure, version examinations/corrections, thinking of Yijing through Zen Buddhism and Ou Yi's academic background. Relatively few of them make a holistic and systematic exposition through the angle of philosophical development of Yijing. And the ontological exposition holds a critical core for philosophy in ＂Zhouyi＂, so from here the paper is to explore the thinking of Zhouyi Chanjie. There's no doubt about the fact that Ou Yi tried to interpret Yijing by Buddhism. However, how did he build up the ontology of Yijing principles by citing Buddhist principles? Were such citations appropriate? Under the architecture of ＂Zhouyi＂, how did he induce Confucianism into Buddhism or the other way round? What characteristics were displayed by such a Buddhist Yijing theory as he had cited and merged? About these issues, this article not only dug deep into the thinking in Zhouyi Chanjie but also tried to find a historical position for Ou Yi's Zhouyi Chanjie on the coordinates of Yijing learning history of thought.