In the early Tang dynasty, the three provinces system was established, and in the middle and late Tang dynasty, the government hall system under the door of Zhongshu was established. The Tang Dynasty is an important stage in the development of prime minister system, and the changes of prime minister institutions and prime minister names are complicated. In the early years of the Tang Dynasty, the prime ministers included Zhong Shuling, governor of Zhongshu Province, Zhong Shi, governor of Xiamen Province, and Shang Shuling, governor of Shangshu Province. The prime minister is an official who assists the emperor in leading major world policies. Later, because Emperor Taizong had served as a minister before he ascended the throne, his generals avoided it, so he took his servant as the governor of Shangshu Province and called him prime minister with ministers and ministers. In the Tang dynasty, because the taste of the prime minister was respected, the master refused to give it to others easily, so he was often regarded as the prime minister and called an official in the name of others. For example, during the reign of Emperor Taizong of Tang Dynasty, Du Yan participated in the state affairs with the official ministers, and Wei Zhi participated in the state affairs with the secretary as the supervisor. Later, it was also called "participation in gains and losses" or "participation in politics", and so on. They were all prime ministers with different names. After Xuanzong kaiyuan, the number of prime ministers decreased, and their positions were more respected, basically full-time. After the Anshi Rebellion, the name of the Prime Minister changed again. Because Zongsheng's generation promoted the calligraphy order in China, and his servants were second-class, he cancelled the title of "Men's Fellow". At the same time, the officials in charge of the secretariat and the servants under the door are basically governors, so it is difficult to set them as prime ministers alone. Therefore, the titles of prime ministers in the late Tang Dynasty are basically "the same thing." The power of the prime minister depends on the attitude of the emperor (and eunuchs in the middle and late Tang Dynasty). In the Tang dynasty, the scope of the emperor's appointment of prime ministers was expanded, not limited to the governors of the three provinces; The increase in the number of prime ministers not only facilitates brainstorming, but also makes them contain each other, thus avoiding the situation of authoritarian ministers. This greatly strengthened centralization and prevented the decline of the emperor's power.