The traditional Chinese "yin/yang" theory has a long history, but there has been difficulty in reconciling the contradictions between different knowledge systems in terms of reflecting the property of yin /yang by the directions of south and north. In the system of Time & Space and Astronomy, yang is matched with south and "yin" with north, while in the system of Yishu (Numbers in the "Yi"), yang is matched with north and yin with south. These two different "yin/yang" notions have profoundly influenced the Chinese culture, and caused troubles in understanding relevant ritual and sacrificial institutions. The diagram of Eight Trigram directions of the "Shifa" (Divination Methods) in the Tsinghua Collection of Bamboo Slip Manuscripts of the Warring States period preserves an unprecedented form of Eight Trigram directions and provides solution to the previous difficulty. In combining archaeological materials with historical documents, this paper explores the issues of "wu-xing" (the five elements) and "yin/yang" formed on the base of the systems of Time & Space, Astronomy and Yishu as reflected in the diagram of Eight Trigram directions of the "Shifa".