His family was from Deng Prefecture (鄧州, in modern Nanyang, Henan) and traced its ancestry to the Northern Wei general Zhao Tong (趙彤).
He served there for over a year, and, because his writing skills were considered excellent, was made the treasurer at Luhun County (陸渾, in modern Luoyang, Henan).
Just several months later, he was recalled to the capital Chang'an to serve as You Shiyi (右拾遺), a low-level consultant at the legislative bureau of government (中書省, Zhongshu Sheng), as well as an imperial scholar.
[5] In 783, Zhao Zongru was made Tuntian Yuanwailang (屯田員外郎), a low-level official at the ministry of public works (工部, Gongbu), and continued to serve as imperial scholar as well.
Emperor Dezong approved of his actions and made him Kaogong Langzhong (考功郎中), a supervisorial official at the ministry of civil service affairs.
Virtually nothing is recorded in history about his acts as chancellor, however, and in 798 he was removed from the post and made a staff member of Emperor Dezong's crown prince Li Song.
Emperor Dezong approved of his carefulness, and in 804 made him the deputy minister of civil service affairs (吏部侍郎, Libu Shilang).
He was thereafter made the military governor (Jiedushi) of Jingnan Circuit (荊南, headquartered in modern Jingzhou, Hubei) as well as the mayor of its capital Jiangling Municipality (江陵).
In 813, he was made the military governor of Shannan West Circuit (山南西道, headquartered in modern Hanzhong, Shaanxi) as well as the mayor of its capital Xingyuan Municipality (興元).
Zhao Zongru opposed on the basis that this was against tradition and that there was no time to revise the examination method before the examinees would be forced to leave the capital.
In 831, when the chancellor Song Shenxi was falsely accused of treason, Emperor Wenzong convened a group of senior officials to discuss potential punishments.