本研究以文本的考察为基础，以郑玄的经学思维和学术方法为手段，以郑玄立说的旨趣为指归，探讨郑玄确立六天说和祀天禘说的思考过程。通过对六天说的的文献依据进行辨析，可知《周礼》中有“昊天上帝-五帝”系统，纬书中有“天皇大帝-五精帝”系统，星象中有“紫微北极星-太微五帝座星”系统。五天帝出自《周礼》，五人帝五人神出自《月令》、《左传》、《尚书五行传》，五精帝出自纬书，郑玄将其结合构成以五天帝为核心的五帝体系；郑玄将《周礼》昊天上帝视为一神，将纬书的天皇大帝与之对应，结合星象中的北极星，构成昊天上帝系统。每一朝代各有五天帝之一作为其感生受命帝，尊于其余四帝。五天帝与昊天上帝构成六帝系统，郑玄的天帝系统实是一天六帝系统。天与帝有别，天以形象言，帝以神灵言，天以体质言，帝以德用言。帝是人格化的，有视听、喜怒、意志，天皇大帝无为无言，五精帝有为有言，五精帝受天皇大帝指使。郑玄以燧人为政教之始；据《春秋元命包》、《春秋运斗枢》以伏羲、女娲、神农为三皇；据《尚书中候》以黄帝、少昊、颛顼、帝喾、尧、舜为五帝。三皇德合天皇大帝，五帝德合五精帝。此为郑玄的帝王谱系说。郑玄取纬书关于帝王谱系诸帝王的感生说，而弃其圣人无父说，将《诗经》的帝王降生视为感五精帝之一即感生帝而生，从而提出了圣人有父，感天而生之说。此为郑玄的感生说。受命由五精帝之一即受命帝主导，一再授予一个神圣家族，其意志记载在《河图》、《洛书》中，受命王获得《河图》、《洛书》或相关的祥瑞为受命的标志。此为郑玄的受命说。郑玄据《春秋纬》、《易纬》等认为天之五精帝代王，每一帝有其德运，五精帝所感生、授命之帝王亦代王，各有德运，其德运是基于五行相生的五德之运，郑玄的帝王谱系的德运与此德运相同，从而将帝王谱系纳入五德运转之中。此为郑玄的五德运转说。郑玄以夏、商、周三正说为出发点，融合天子存二王后之说，以及王者禘其祖之所自出之说，提出“所存二王之后者，命使郊天，以天子之礼祭其始祖，受命之王自行其正朔服色”，即通天三统之说。郑玄以其“帝王易代，莫不改正”之说为标准，推演出帝王谱系诸帝王的三统之色，从而将帝王谱系纳入三统改复之中。此为郑玄的三统改复说。

This study is based on a textual survey, using Zheng Xuan's classics and academic methods as means, and Zheng Xuan’s purported goal as the point of view, to discuss Zheng Xuan’s Six-Tian theory (六天说) and his thinking process.Through the analysis of the literature basis of the Six-Tian, it can be seen that in the Zhou-Li (《周礼》), there is a system of “Tian God-Five Tian Emperors” (“昊天上帝-五帝”), and in the Weft-Books (纬书) system, there is a system of “Heavenly God-Five Jing Emperors” (“天皇大帝-五精帝”), and in the Astrology, there is a system of “Polaris-Five Emperors Stars" (“紫微北极星-太微五帝座星”). The Five Tian Emperors come from the Zhou-Li, the Five Human Emperors and Five Human Courtiers come from the Yue-Ling (《月令》), the Zuo-Zhuan (《左传》) and the Shang-Shu-Wu-Xing-Zhuan (《尚书五行传》), and the Five Jing Emperors come from the Weft-Books. Zheng Xuan combined them into a five emperors system with the five-tian emperors as its core. Zheng Xuan regards the Heaven as a god, corresponded it with the God in the Weft-Books, and combined them with the Polaris to form the system of Tian God. Each dynasty has one of the Five Tian Emperors as its inducing and commanding emperor (感生受命帝), which is more honored than the other four Tian Emperors. The Five Tian Emperors and the Tian God form the system of the Six Tian Emperors system. Actually, Zheng Xuan’s system of Emperors is a system of “one Tian-Six Emperors”. Tian is different from Tian Emperor. The Tian Emperors are personified, with vision, hearing, anger and will. The Tian God is inactive and speechless, while the Five Tian Emperors are active and can speech. The Five Tian Emperors are instructed by the Tian God.Zheng Xuan regarded Sui Ren (燧人) as the beginning of politics and history. Zheng Xuan regarded Fu Xi (伏羲), Nv Wa (女娲) and Shen Nong (神农) as the Three Emperors according to the Chun-Qiu-Yuan-Ming-Bao (《春秋元命包》) and the Chun-Qiu-Yun-Dou-Shu (《春秋运斗枢》). Zheng Xuan regarded Huang Di (黄帝), Shao Hao (少昊), Zhuan Xu (颛顼), Di Ku (帝喾), Yao (尧) and Shun (舜) as the Five Emperors according to the Shang-Shu-Zhong-Hou (《尚书中候》). The Three Emperors’ morality can be compared with the Tian God, and the Five Emperors’ morality can be compared with the Five Emperors Stars. This is emperors’ lineage of Zheng Xuan. Zheng Xuan accepted the Weft-Books’ Gan Sheng theory (感生说) about the emperors’ lineage and abandoned its saint’s fatherless theory (圣人无父说), and considered the mythology of the emperors’ birth in the Book of Songs (《诗经》) as a heavenly sensation, thereby raising the theory that a saint has a father and is generated by Tian. This is Zheng Xuan’s Gan Sheng theory. Shou Ming (受命) is conducted by the Shou Ming Emperor, one of the Five Tian Emperors, who repeatedly grants Tian Ming (天命) to a holy family. Shou Ming Tian Emperor’ will is recorded on the He-Tu (《河图》) and Luo-Shu (《洛书》), and obtaining the He-Tu, Luo-Shu or related auspicious omen is the sign of acceptance of Tian Ming. This is Zheng Xuan's Shou Ming theory. According to the Chun-Qiu-Wei (《春秋纬》) and Yi-Wei (《易纬》), Zheng Xuan believed that the Five Tian Emperors governed the heaven alternatively, each emperor had his own virtues, and the emperors and kings the Five Jing Emperors induced and commanded govern the earth alternatively, also. This is based on the five virtues of the five elements (五行). Zheng Xuan’s emperors’ lineage is the same as the five virtue, so that the emperors’ lineage is absorbed into the circulation of the five virtues. This is Zheng Xuan’s Five Virtues’ Circulation theory (五德运转说). Zheng Xuan used Xia (夏), Shang (商), and Zhou (周) as his starting point to construct the theory of the emperor’s saving two emperors’ descendants, and the emperors Di (禘) the Tian emperors that the emperors’ ancestors derived from. He proposed that the two emperors’ descendants, as emperors, should sacrifice to the Tian Emperors. This is the theory of the Three Systems (三统). Using his theory of “each emperor changes the first month of lunar year”, Zheng Xuan inferred each emperor’s first lunar month, thus embedding the emperors’ lineage into the theory of Three Systems’ Circulation (三统改复说).Zheng Xuan distinguished the Yi-Wei-Qian-Zao-Du (《易纬乾凿度》) “the three kings sacrifice to the Tian Emperors on Xia’s first lunar month” from the Da-Si-Yue (《大司乐》) “sacrifice to the Tian God on Yuan Qiu (圜丘) at winter solstice”, and established the theory of difference between Yuan Qiu and Southern Suburb (南郊). Zheng Xuan took Zhou’ Southern Suburb and Qi Gu (祈穀) as one, and laid Plowing (籍田) behand it, which were all held in Xia’s first lunar month, and thus established the theory of regarding Southern Suburb and Qi Gu as one. Zheng Xuan regards sacrificing to the Tian Emperor on Zhou’s first lunar month in the Jiao-Te-Sheng (《郊特牲》) and the Ming-Tang-Wei (《明堂位》) as Lu Li (鲁礼), and distinguished it from Zhou’s Yuan Qiu and Southern Suburb, thus established the theory of difference between Zhou Li and Lu Li (周鲁为二说). Zheng Xuan regarded Lu’s Southern Suburb and Qi Gu as one, which were held on Zhou’s first lunar month. If the animal sacrifice is damaged, the rite would be postponed to the second or third month. Zheng Xuan used the Gu-Liang-Zhuan (《穀梁传》) to explain the uncertainty of time of Lu’s Southern Suburb, thus established the theory of Lu’s Southern Suburb as one. Zheng Xuan combined the theories of difference between Yuan Qiu and Southern Suburb, difference between Zhou Li and Lu Li, regarding Southern Suburb and Qi Gu as one and the Six-Tian system together to construct Zhou’s Yuan Qiu Li and Southern Suburb Li. Zheng Xuan combined the theories of difference between Yuan Qiu and Southern Suburb, difference between Zhou Li and Lu Li, Lu’s Southern Suburb as one and the Six-Tian system together to construct Lu’s Southern Suburb Li. Zheng Xuan distinguished the Southern Suburbs of the two emperors’ descendants and Zhou’s and Lu’s Southern Suburbs, thus established the Southern Suburbs of the two emperors’ descendants. Therefore, Zheng Xuan’s Di (禘) system included Yuan Qiu Di and Southern Suburb Di (divided into Southern Suburbs of Zhou, Lu, and the two emperors’ descendants). The key component of Zheng Xuan’s Southern Suburb Di theory is the combination of ancestors and Tian, which is of great significance for the continuity of Heaven and humanity and the operation of politics and history. Zheng Xuan accommodated the theories of Six-Tian theory, emperors’ lineage, Gan Sheng, Shou Ming, Five Virtues’ Circulation and Three Systems’ Circulation in his Di theory, thus displayed a complete prospect of politics and history about the combination of heaven with human.