His family was originally from what would become Hua Prefecture (滑州, roughly modern Anyang, Henan), but by Li Yuanhong's time had moved to the Tang dynasty capital Chang'an.
Li Yuanhong's great-great-grandfather Bing Ming (丙明) served as a commandant during the Sui dynasty and was created the Duke of Longju.
In 725, the deputy ministers of census (戶部侍郎, Hubu Shilang) Yang Chang (楊瑒) and Bai Zhishen (白知慎) were both charged with making poor budgetary decisions and demoted to be prefectural prefects.
It was said that Li was honest and frugal, and after he became chancellor, he, with some success, tried to curb the tendency for officials to seek promotions by bribes or ingratiations.
Meanwhile, the official Wu Jing (吳兢) had been in charge of editing the imperial history, but before his work was complete, he took a leave because of his mother's death.
Li believed that having Wu and Zhang work separately in separate locations, rather than at the History Pavilion (史館, Shiguan) that Emperor Xuanzong's great-grandfather Emperor Taizong had established, made it easy for imperial archives to be lost, and at his suggestion, Wu and Zhang were asked to work together at the History Pavilion.
It was said that while Li served as chancellor, he did not get a larger mansion, did not get more impressive horses, and gave the imperial awards to his relatives, drawing praise from the senior official Song Jing.
He later left civil service altogether on account of illness, but later was given the honorary office of minister of census and allowed to retire with that title.