《清華簡．筮法》的〈釋文〉顯示，戰國時在受南方楚文化影響的地區，存在著一支占筮術士的傳承系統。此系統的卦畫，建基於四個三爻卦，每一爻各用六個數字分判；整個三爻卦卻連繫上《周易》的八經卦。基於〈釋文〉所顯露的各種資訊，本文判斷此系統的傳承源流，或許早於《周易》，可能與《周易》有共同的祖先。本文認為：現存的〈說卦傳〉文本，已經包含太多後出的因素（為配合《周易》的傳承而添入），因此不足以作為解釋〈筮法〉的基準。

The recently published annotation of the ＂Shifa＂ 筮法, which appeared in the Tsing Hua Bamboo Manuscripts (Tsing Hua jian 清華簡), indicates that during the Warring States there existed in the south (the area influenced by Chu 楚 culture) a long-standing tradition of divinatory art (zhanbu 占卜) based on the eight trigrams (bagua 八卦). The fortune telling practice described in the text used four of the trigrams, which were each comprised of three numerical strokes (shuzi yao 數字爻). This article argues that while this tradition bares some resemblance to that of the Book of Changes (Zhouyi 周易), its origin is actually much older. For this reason, the Book of Changes' ＂Shuogua zhuan＂ 說卦傳 commentary is not useful for interpreting the ＂Shifa＂, as is conventionally claimed.