本文試由朱熹易學對程伊川易學的承繼、改造及創新中，來對比兩人易學的相同處與差異處，並說明其間差異的所以然之由。文中分述兩人對儒家經學及《易》書的研究價值觀。對比兩人對《易》書的研究取向與注疏方法之對比，兩人研易著《易》的歷程。朱熹對伊川易學繼承處主要在採取以義理注《易》的形式，承順儒家易的路數重人事的訓誡、生生不已的動態本體觀、體在用中及理在象中的存有論、一陰一陽的對待說與流行說、以「道」、「氣」釋形而上與形而下的存有層級。文中也羅列了，朱熹易學與伊川易學的重大差異有六端。一是伊川不重視易占及貶抑術數中的風水地理說，朱熹皆與以正視與解說；二是伊川易以中道為貴，朱熹易主陰陽相勝的變易義；三是伊川易側重義理解《易》的具體性與殊別性，朱熹較重視普遍的形式原理；四是朱熹易在訓詁考證的功夫上勝於伊川易；五是朱熹易的內容包容性較大，規模周備，且不像伊川易般的重視〈序卦傳〉；六，朱熹易特別強調周濂溪的〈太極圖說〉，尤其是「大極」概念，伊川易則全然不提及。

　　　　　This paper is intended to compare Zhu Xi's and Cheng Yi-chuan's Yi theories in terms of how Zhu succeeds, refashions, or recreates Cheng's theory; it is also explained why Zhu and Cheng are different. We show firstly how they value Confucianism and Yi Jing and compare their different approaches to and annotations ofYi Jing as well as the developments of their respective studies ofYi Jing. The things Zhu inherits from Cheng are mainly: Cheng's annotation ofYi Jing in terms of meaning, the Confucian approach to Yi Jing with its emphasis on human lives, the everlasting dynamic ontology, the coordination of Ying and Yang, and the interpretation of the ontological hierarchy in terms of Dao and Qi. Besides, there are six differences between them as well: first, Cheng disregards augury and the theory of Feng-shuei as a kind of pseudo-science, while Zhu respects and explains these theories; second, Cheng values the middleway while Zhu appreciates the transformation of Ying and Yang; third, Cheng emphasizes on particularity and specificity while Zhu prizes universality; fourth, Zhu is superior to Cheng in the field of exegetics; fifth, Zhu's theory of Yi is more encompassing, while Cheng treasures only Xu Gua Zhuan; sixth, Zhu highly appreciates Zhou Lian Xi's Tai Ji Tu Shuo, especially the idea ofTai Ji, while Cheng doesn't even mentions it.