|| ‘Zhouyi’ is a very important scripture in Chinese culture. As time went by, there are many different explanations of ‘Zhouyi’ over the several thousand years. However, Mao Qiling created his own system, ‘Zhongshi yi’, to explain ‘Zhouyi’ based on all the other explanations. Therefore, this thesis define Zhongshi yi ‘s status in the Yi’s history by treating Zhongshi yi’s contents, viewpoint, and system to explain Yi through researching on ‘Zhongshi yi’ mainly and other books such as ‘Tueiyi Shihmo’ and ‘Chunqiu Jhanshih Shu’.There are six chapters in this thesis. The first chapter is ‘introduction’ introducing the motive, target, method, and scope of this thesis. Also, it reviews other’s research results in order to outline the content of this thesis. ‘Introducing to “Zhongshi yi”’ is the second chapter. This chapter describes the feature of ‘Zhongshi yi’ in detail by three ways: the background to create ‘Zhongshi yi’, the outline of Zhongshi yi’s content, and the characteristics of writing style in ‘Zhongshi yi’. Then, the third chapter is ‘delving into the Zhongshi yi’s way to explain classics’. It mainly discusses the way that Mao use in the ‘Zhongshi yi’ to explain classics, including ways explaining Yi by all other classics, proofing Yi by history, and explaining Yi by ‘yanyisicih’. Continuing the discussion of ‘yanyisicih’, the way to explain ‘Yi’, in the third chapter, the forth chapter is ‘the theory of deducing Yi in “Zhongshi yi”’ (part 1) - discussing the essence of deducing Yi ’ that delve the core tought of ‘Zhongshi yi’, the theory of deducing Yi. This chapter defines the theory of deducing Yi as the essence of a theory that is systematic rules of change between hexagrams by discussing the contents of ‘buyiqua’、 ‘jyuqua’、 ‘banjyuqua’、‘zihmuyiqua’、 ‘fenyiqua’. The application of Mao’s theory of deducing Yi is the fifth chapter, ‘the theory of deducing Yi in “Zhongshi yi”’ (part 2)-delving the divinatory methods and their application’. This chapter discussing the relationship between divinatory methods and the theory of deducing Yi from divinatory methods in every qua. The sixth chapter is ‘conclusion’ to conclude the result in the thesis. In addition, this chapter criticize Mao’s ‘Zhongshi yi’ and fairly give it the status in Yi’s history.