開元20年（732）《大唐開元禮》的編纂標誌著唐代禮儀制度的集大成，且對「天」的定義做出了總結。本文討論唐前期國家型態，以及統治秩序中君臣關係之間的相聯性，便以《大唐開元禮》中郊祀禮的「進熟」儀式為切入點。自隋代立國展開中央集權的強化，官員一由中央任命，皇帝擺脫了自漢代以來的「二重君主觀」，同時也與全體官員直接聯繫，在「公家」中締結一元化的君臣關係並「共治天下」。李唐王朝鑒於隋代覆亡之速，君臣關係的整合與釐清，成為唐初的君主所注重的課題。從太宗與臣下對唐代國家政治結構的討論均以「公」為出發點，可看出官員在郡縣制與選舉制度下恪盡職守對百姓生計以及穩固國家統治的重要；皇帝（天子）在郊祀禮中對天地鬼神與宗廟祖先的「臣服」，使「天下一家」的國家為「公」領域的圖像透過禮儀而構成。最後，唐代皇帝提倡的「君臣一體」關係，在隋唐「二重君主觀」消融的國家型態下化為實際並更加緊密，雙方在尊卑確立的前提下各盡義務共治天下；郊祀禮中皇帝溝通天地，而從祀群官透過皇帝為媒介與「天」共食交流，不但象徵著上下協力的君臣關係，也呈現了皇帝權力與統治秩序的面貌。

The compilation of ＂Datang Kaiyuan Ceremony＂ in the 20th year of Kaiyuan marks the milestone of the Tang Dynasty ritual system, and made the definition of ＂Heaven＂ a summary. The author focuses on the ＂Jin-Shu (進熟)＂ ritual in ＂Datang Kaiyuan Ceremony＂ as a starting point to discuss the political structure of Tang Dynasty, as well as the connection in the Emperor-Subject Relation within the ruling order. Since the Sui Dynasty strengthened the degree of centralization, all the government officials are appointed by the imperial administration, and the emperor establishes the unified Emperor-Subject Relation to ＂co-manage under Heaven＂ with the officials. In view of the collapsing of the Sui Dynasty, the integrating of Emperor-Subject Relation becomes a primary issue to the emperors of the early Tang Dynasty. From the discussions of political structures between Tang Taizong and his subjects are all based on the point of ＂public,＂ the full functioning of the officials in the bureaucracy has been proved to be important to the livelihood of people and the stabilization of the state. When the emperor ＂declares himself a subject＂ to Heaven, Gods and the Ancestry, the pattern of ＂One Family under Heaven＂ as ＂public＂ is shown through the ritual system. After the collapsing of ＂The Double Concepts of Monarchy＂ in the Sui Dynasty, ＂The Unity Relationship between Emperors and the Subjects＂ communicates with Heaven while the officials communicate with Heaven through the emperor in the State Sacrifice of Jiao, not symbolizes the Unity Relationship between Emperors and the Subjects, but shows the power of emperor and the ruling order.