This article studies on the meaning of Chinese ten heavenly branches and twelve earthly stems, especially on the Chinese characters of 干 and 支. 干支 had been used from the ancient Chinese Yin(殷) period. The meaning of characters had been changed and expanded especially during 漢 period. 干 and 支 were not the same characters originally made, which were 幹 and 枝. 幹枝, usually called during the 漢 period, had interacting function, such as, heaven and earth, yin and yang, sun and moon, mother and son, and finally branch and stem. 干支 were considered the characters of just provisional accommodation, which commonly useful method in ancient Chinese characters. Each ten heavenly branches(十干) and twelve earthly stems(十二支) have repeating circulations on their calendars. And also their least common multiple sixty 甲子 has its own repeating circulation.