In 805, Tang Dezong died, and the crown prince Li Yu succeeded to the throne, that is, Tang Shunzong. The problems left by Tang Dynasty Sect became more and more serious, and Tang Shunzong and Tang Xianzong both tried to solve them, among which Tang Xianzong was more successful and realized Yuan and Zhongxing.

Tang Shunzong took Wei Zhiyi as the prime minister and enabled the reformers headed by Wang Shuwen. They abolished the palace market and Wufang Xiaoer, which oppressed the people, and reduced taxes.

Ren Hantai took control of the Shence Army and tried to seize the power of the eunuchs, which is known in history as Yongzhen Innovation. In the same year, Tang Shunzong suffered a stroke, and the eunuch Ju Wenzhen took advantage of the psychology of the crown prince Li Chun to want to be the emperor, and united with Wei Gao and other feudal towns to force Tang Shunzong to abdicate, so as to overthrow the reformers, known as Yongzhen Neizen in history.

The crown prince Li Chun succeeded to the throne, that is, Tang Xianzong. Tang Xianzong was quite able to control the eunuchs and the outer court, worked diligently in government affairs, and was good at accepting advice.

He took Du Huangsheng's suggestion and set about cutting the domain. At that time, there were 46 feudal towns in the country, most of which were semi-independent, and only the area around Zhejiang still supplied the financial resources of the imperial court.

He adopted a widening of financial channels and practised frugality in order to stabilize his financial resources. Since the Yi'an history system was the strongest among the feudal towns, he started with the weaker feudal towns.

In 806, Liu Pi, the deputy envoy of Jiannan Xichuan Jiedu, Yang Huilin and Li Qi of Zhenhai in the following year rebelled successively and were pacified by the Tang dynasty one by one.

In 814, due to Wu Yuanji's plundering and private succession, Tang Xianzong successively sent troops from 16 towns to defeat it, but it was unsuccessful.

During this period, Li Shidao of Ziqing and Chengde Wang Chengzong sent people to assassinate Wu Yuanheng, the prime minister of the main battle faction, and the Tang Emperor replaced him with Pei Du, and used Li Su (Li Sheng's son) to discuss the war.

In 817, Li Sue adopted the plan of the general Li You, and attacked Wu Yuanji's headquarters in Caizhou in the snow, and Huaixi was pacified.

Ziqing Li Shidao panicked, and Tang Xianzong sent Li Guangyan and Li Su to lead the army to crusade. Two years later, Li Shidao was killed by his subordinates, and Ziqing was pacified.

On the Hebei side, Wei Botian Hongzheng supported the Tang Dynasty. Chengde Wang Chengzong once rebelled against the Tang Dynasty, and after Huaixi was pacified, he and Lu Long and Liu returned to the Tang Dynasty.

By 819, the feudal towns of the whole country were nominally subordinate to the central government, and sent envoys to pay tribute, which was known as Yuan and Zhongxing in history.

However, Tang Xianzong was a bit lazy about state affairs and liked to build mansions. He worships Buddha very much, and once went to Famen Temple to welcome the Buddha's bones, and Han Yu advised him and was degraded.

In 820, Tang Xianzong was poisoned by eunuchs in Daming Palace, and the three towns of Hebei rebelled, and the Zhongxing period ended.

In 821, President Lu Long and Liu resigned, and the Tang family sent Zhang Hongjing to take over. Zhang Hongjing mismanaged, and Lu Longbing supported Zhu Kerong's rebellion.

Tian Hongzheng, who moved to Chengde, was killed by the general Wang Tingcuo. Wei Bo Tianbu (Tian Zhenghong's son) was forced to die by the army, and Wei Bojun supported Shi Xiancheng's rebellion, so far the three towns of Hebei rebelled.

When Hebei did not rebel, ministers Xiao Li and Duan Wenchang suggested that the country should be disarmed. Now the retrenched soldiers have all defected to the three towns of Hebei, fueling their momentum.

However, the three towns of Hebei did not continue to be strong after that, and during the period of Tang Jingzong and Tang Wuzong, most of the three towns of Hebei were subject to their strong troops, and sometimes they were usurped by their subordinates, which was far less than the original dominance.

The feudal towns in various regions were still under the orders of the central government until the Huangchao Rebellion. Most of the political power in the central Tang Dynasty was controlled by the emperor and the prime minister, but after Tianbao, it was transformed into a union between the emperor and the eunuchs of the inner court, and the prime minister of the outer court became a second-rate political role.

After the Jingyuan Mutiny, the emperor no longer trusted the military ministers, and the eunuchs were more in control of the central forbidden army. The Yongzhen Neizen incident enabled the eunuchs to successfully defeat the outer court and scholars.

The eunuchs who controlled the military and political power became the behind-the-scenes controllers of the central government, and most of the emperors after Tang Xianzong were arbitrarily deposed by the eunuchs.

In 820, Tang Xianzong was poisoned by the eunuch Chen Hongzhi, and the eunuch Wang Shoucheng was behind this incident.

Wang Shoucheng supported the crown prince Li Huan to succeed to the throne, that is, Tang Muzong. After he ascended the throne, the three towns of Hebei rebelled, and the Niu Li party struggle controlled by the eunuchs also intensified.

Tang Muzong died three years after ascending the throne, and was succeeded by his son Li Zhan, that is, Tang Jingzong, and the power was still controlled by Wang Shoucheng.

Tang Jingzong also ignored the government and politics, and specialized in amusement and batting. In 826, Tang Jingzong went out

"Fighting the night fox", after returning to the palace, he held a banquet and was killed by the eunuch Liu Keming. Liu Keming intends to seize the power of Wang Shoucheng and support Li Wu, the king of Jiang.

When Wang Shoucheng learned of this, he used his troops to meet Li Han, the son of Tang Muzong, and killed his political enemies. Li Han succeeded to the throne, that is, Tang Wenzong.