Liu Congyi was born in 742, during the reign of Emperor Xuanzong. He came from a line of officials of Tang Dynasty, starting with his great-great-grandfather Liu Linfu. His great-granduncle Liu Xiangdao served as a chancellor during the reign of Emperor Gaozong, and Liu Xiangdao's son Liu Jingxian served as a chancellor late in the reign of Emperor Gaozong as well as the regency of Emperor Gaozong's wife Empress Dowager Wu over their sons Emperor Zhongzong and Emperor Ruizong. Liu Congyi's grandfather Liu Lingzhi served as a deputy minister, while his father Liu Ruzhi served as the deputy mayor of Jingzhao Municipality, which included the Tang capital Chang'an.
During Emperor Daizong's reign
Liu Congyi himself passed the imperial examinations when he was young, and during the Dali era of Emperor Xuanzong's grandson Emperor Daizong, he passed a special examination for those who could write in a grand style. He was thereafter made Xiaoshulang, an editor at the Palace Library. He subsequently served as the sheriff of Weinan County. Because his behavior was elegant, he was respected by the official Chang Gun, and after Chang became chancellor in 777, he made Liu Jiancha Yushi, an imperial censor. Later, though, when Liu's mother died, he left governmental service to observe a period of mourning for her.
During Emperor Dezong's reign
When Liu Congyi's mourning period was complete, the emperor was Emperor Daizong's son Emperor Dezong, and the most powerful chancellor was Lu Qi. Lu recommended Liu, and Liu returned to the bureau of censors as Shiyushi. After several months, because a relative of his was also becoming an imperial censor, under Tang regulations that relatives should not serve at the same agency, he was made Xingbu Yuanwailang, a low-level official at the ministry of justice. In 783, with Li Xilie the military governor of Huaixi Circuit rebelling against imperial rule, Emperor Dezong, believing that the armies sent against Li Xilie needed a supreme commander to coordinate their actions, commissioned his son Li Yi the Prince of Pu to be the supreme commander of the forces against Huaixi, and he made Liu a secretary for Li Yi. However, before Li Yi could depart Chang'an, soldiers from Jingyuan Circuit, at Chang'an to await deployment to the east against Li Xilie or other warlords, mutinied after they were not awarded as they believed they deserved. Emperor Dezong fled to Fengtian. Many officials followed him there, including Liu. The Jingyuan soldiers supported the general Zhu Ci as their leader, and Zhu soon claimed imperial title of his own state of Qin, competing with Emperor Dezong. While Emperor Dezong was thus kept at Fengtian, he made Liu the deputy minister of justice and gave him the designation of Tong Zhongshu Menxia Pingzhangshi, making him a chancellor de facto, along with Xiao Fu and Jiang Gongfu. When Emperor Dezong was forced to further flee to Liang Prefecture in 784, he made Liu Zhongshu Shilang, the deputy head of the legislative bureau, and continued to have Liu serve as chancellor. It was said that Liu was much liked by Emperor Dezong and was known for being careful and virtuous personally, but did not help Emperor Dezong correct his ways. After the general Li Sheng destroyed Zhu's regime later in 784 and allowed Emperor Dezong to return to Chang'an, there was an incident in which Xiao, who had just returned from a mission to survey the southern circuits, recommended that Chen Shaoyou, the military governor of Huainan Circuit, who had submitted to Li Xilie during the time Emperor Dezong was away from Chang'an, be replaced by Wei Gao — a Fengxiang officer who had resisted Li Chulin. Emperor Dezong agreed. He sent the imperial eunuch messenger Ma Qinxu to inform Liu and ask Liu to discuss this matter with Xiao without consulting fellow chancellors Li Mian and Lu Han. However, Xiao was surprised by this, and, finding it inappropriate that Emperor Dezong was keeping secrets away from Li Mian and Lu, as fellow chancellors, stated: When Liu informed Emperor Dezong about this, Emperor Dezong was displeased. Xiao, seeing that he had lost the emperor's favor, resigned. Further, when Emperor Dezong tried to promote Lu Qi, who had been exiled after being blamed for causing Zhu's rebellion, in 785, and the imperial attendant Yuan Gao objected, Liu and Lu Han did not dare to support Yuan's position. Yuan had to protest the decision along with several of his junior colleagues and finally prevailed on Emperor Dezong to change Emperor Dezong's mind. Liu grew ill in late 785 and offered to resign. On November 3, 785, Emperor Dezong removed him from his chancellor position and made him the minister of census. Liu died the next day and was publicly mourned.
