原始五行說非指金、木、水、火、土之五物，而指歷數一、二、三、四、五之五時，起源於十、五以分周天一歲（取整360日）的十月制（十干）古曆法，與陰陽、四時、八正等概念同構，屬於天文天象學的天道論體系；金、木、水、火、土則本是原始五材說的真實內涵，是樸素的物質構成論。鄒衍等在思孟學派以人間五德比附天道五行說之後，「以材比德」地將人間金、木、水、火、土的生剋性能與天道五行歷數的變替循環附會對配而張「五德終始」論，五材說遂鳩占鵲巢地進入了歷數五行的天道論系統並作金、木、水、火、土概念的根植及泛化。中國科學院天文曆法史專家陳久金在彝族十月制舊曆法的啟示下對「五行」概念本義的探析是成功的，這不僅解決了古代十月制太陽曆的基本歷數問題，而且「五行」這一中國思想史上的重大概念、重大問題也獲得了正本清源的本義之破解。本文在陳久金9條有效證據的基礎上，詳證「五行」本是天文學意義上的天道歷數概念。

In the origin of Chinese “Wu-xing (五行)” theory, “Wu-xing” is not concept of materials such as gold, wood, water, fire, and earth. In fact, the earliest meaning of “Wu-xing” is concept of calendar adopted to describe the zodiac or the time, “Wu” refers to five, “Xing”refers to the operation of the sun or the zodiac. Yin-yang (陰陽), Si-shi (四時), Ba-zheng (八正) , and “Wu-xing” , all belong to the theory system which are descriptions of heavens or solar terms. In the earliest time, gold, wood, water, fire, and earth do not belong to the concept of “Wu-xing” , but belong to the concept of “Wu-cai” (五材) which means five elements of material in the universe. Si-meng (思孟) school drew an analogy between human five virtues and Wu-xing of zodiac, than Zouyan (鄒衍) contributed to compare the five moralities which were called “gold, wood, water, fire, earth” to the heaven, and referred to the alternate circulation of the heaven. According to the Yi (彝) nationality ancient calendar which the integer 360 of days in a year was divided into 10 months or 5 sections, Chen Jiujin (陳久金), an exper on the history of astronomy at Chinese Academy of Sciences, correctly analyzed the original meaning of “Wu-xing” which is a major concept or major issue in the Chinese ancient thought. This not only solved the basic problem of listing ten months for ancient solar calendar, but also received thorough solution to “Wu-xing” ’s original meaning . Based on Chen Jiujin’s 9 valid evidence, this paper will give a detailed proof of the “Wu-xing” which originally means five or ten periods of the zodiac or the year.