Li Chun, formerly known as Li Chun, was the eldest son of Shunzong. In 805, he was established as Crown Prince with the support of eunuchs and vassal towns. In August of the same year, he ascended the throne with accession following abdication, and was changed to Yuan Yuanhe the following year. Taking his grandfather Dezong's appeasement of the feudal towns as a warning, he determined to restore the authority of the central government. When he came to the throne, he put down the rebellion of Liu Pi in Xichuan and Li Qi in Zhenhai, and appointed capable ministers such as Du Huangshang, Li Jifu, Pei Du, and Wu Yuanheng to rectify the finances.
In 814, Wu Yuanji inherited Huaixi without permission, and Xianzong insisted on using troops. In 815, chief minister Wu Yuanheng was assassinated by assassins in the feudal town. Many people in the DPRK advocated a strike, but he still presided over the war with Pei Du as prime minister. In 817, Li Su made a surprise attack on Caizhou on a snowy night and captured Wu Yuanji. After that, King Chengde offered his land and asked for surrender, and Cheng Quan of Henghai moved his family to the dynasty. In 819, Li Shidao of Ziqing was killed by his generals, and all the vassal towns in various places obeyed orders for a while, which was called "Yuanhe Zhongxing" in history.
Xianzong was extravagant and complacent in his later years. He appointed ministers to gather the Buddha's bones in Famen Temple and took elixirs. He had a bad temper and the eunuchs on his left and right were often killed for minor offenses. In the first month of 820, he died violently in Zhonghe Hall. It is generally believed that he was killed by the eunuch Chen Hongzhi and others. The eunuchs immediately supported Crown Prince Li Heng.
Xianzong is the most accomplished Tang dynasty emperor after An Lushan Rebellion. He persisted in cutting down the vassal vassal, employed people appropriately, and successively pacified Xichuan, Zhenhai, Huaixi, and Ziqing despite financial difficulties, temporarily ending the separatist rule of vassal towns and restoring the prestige of the imperial court. However, Yuanhe Zhongxing mainly relied on force and temporary momentum, and did not eradicate the soil of the vassal town; he also reused eunuchs, worshiped Buddha and sought immortality in his later years, and eventually died at the hands of the eunuchs, and the achievements of Zhongxing were quickly lost after his death.