Both of the three Um and three Yang and the six hyo(六爻) of Iching are based on Um and Yang theory and five phases theory. This paper is about mutual relation of them. First, every change in the universe is induced by Un and Ki. Un is the nature that things have their own. Ki is surroundings that things change in. Second, Un and Ki are not separate things. That is they are generated by each other. Third, both of them are the signs of change which means they are similar. The first Hyo (初爻) and Kwolum-pungmok(厥陰風木), the seond Hyo(二爻) and Soum-gunhwa(少陰君火), the third Hyo(三爻) and Teum-supto(太陰濕土), the forth Hyo(四爻) and Soyang-sanghwa(少陽相火), the fifth Hyo(五爻) and Yangmyung-zogum(陽明燥金), and the sixth Hyo(六爻) and Teyang-hansu(太陽寒水) have similar principles. It is important to make clear up their meanings and mutual relation.