He started his official service career as the civil service officer (司功參軍, Sigong Canjun) at Bo Prefecture (亳州, roughly modern Bozhou, Anhui), and later served as Simen Yuanwailang (司門員外郎), a junior official at the ministry of justice.
Yang thus had him sent out of the capital Chang'an to serve as the governor of Baxi Commandery (巴西, roughly modern Mianyang, Sichuan).
Meanwhile, though, Emperor Xuanzong, unaware of this, was still exercising imperial authority, and on his way to Chengdu made Fang Guan a chancellor.
(Cui's biography in the Old Book of Tang claimed that Cui overly listened to his subordinates, who accepted bribes to recommend people,[3] while his biography in the New Book of Tang, which was less critical of him, claimed that he was willing to select people that he knew without fear that he would be accused of nepotism, but was nevertheless not very good at selecting candidates.
[4]) In fall 757, Emperor Suzong removed him from his chancellor position and made him the governor of Yuhang Commandery (餘杭, roughly modern Hangzhou, Zhejiang), as well as the examiner and commander of the region east of the Yangtze.
At a later point, after Tang forces had recaptured Chang'an, Cui Huan was recalled to the capital to serve as deputy minister of civil service affairs (吏部侍郎, Libu Shilang).
Yuan's associate Zhang Qing (張青) argued that this was inappropriate, and Emperor Daizong had Cui investigated and interrogated.
Cui had no response to the accusations and was demoted to be the prefect of Dao Prefecture (道州, in modern Yongzhou, Hunan).