以「數」高度聯結《易》說為宋代易學的重要特色，尤其將「數」與易學圖式進行結合，為北宋以來《易》說的創造性理解。丁易東專著《大衍索隱》，以傳統大衍之數的概念為基點，廣摭諸家之言，並自創新說，制成龐富的大衍圖式，提出規模周全的大衍之說，並將數值運用發揮的淋淋盡緻。丁氏確立衍數與天地之數的關係，並以衍數建構出不同於朱熹以降普遍使用之筮法，也將衍數與河洛之學作嚴密的聯結。本文以丁易東大衍之數聯結圖書之學為核心，從大衍推筮的改造與「一」的認識觀、大衍筮數的形成與結構、大衍合天地之數的陰陽相生與互根圖說、大衍變化的具體時空圖式，以及大衍變化與《河圖》和《洛書》之聯結等方面，探討其大衍學所展現出的具體內容，乃至所傳達的圖書易學史之重要意義。

ne of the important characteristics of Yixue in the Song Dynasty (宋代）is the interpretation of Yi with numbers. The combination of numbers and Yi-diagrams (易圖）is an innovation of the Northern Song Dynasty (北宋）■
Ding Yidong,s( 丁易東）Y7 Xiang Yi discusses the change in number values, which reflects his thoughts on change. Based on traditional concept of the Dayan numbers (the numbers of the Great Expansion) (大衍之數),Ding proposes an innovative and complex Dayan theory and diagrams in Dayan Suoyin (大衍索隱),putting number values into application. Ding establishes the relationship between the Dayan numbers (大衍之數)and the numbers of heaven and earth, and makes a close connection between the Dayan numbers (大衍之數) and the theory of He-Luo (河洛). Focusing on the connection Ding makes between the Dayan numbers (大衍之數)and the theory of Tu-shu (圖書),this study aims to provide a detailed analysis and interpretation of Ding’s diagrams, explore the essence of his Dayan theory and the significance of the development of Tu-shu (圖書).