During the reign of Külüg Khan, Bayan was appointed a few different positions in the court. He became a Darughachi in the year of 1309. Bayan held several provincial posts during the reign of Ayurbarwada Buyantu Khan. Namely the Tong Pingzhangshi (Vaguely, the "vice prime minister") of Jiangzhe province, Jiangxi province and Henan province. It is said that he did not tolerate any local bullies who took advantage of the poor.
At the turn of the 13th/14th centuries he, together with the Turk El Temür, was a member of the group around Qaishan, a nephew of Temür Khan who was appointed to defend Mongolia against the Chagatai Khanate under Kaidu, the grandson of Ögedei. In one battle, he repelled and chased the Ögedeid army; and was given the title of Baghatur. After Temür's death, Qaishan emerged as the new Yuan emperor, and Bayan was among those who received an official position as a reward. Later, Bayan was governour of Henan. Historians describe him as a traditionalist who attempted to preserve Mongolian culture while he is seen as a violent aristocrat by some. Bayan Khutugh was his niece.
In 1328. Bayan had rendered great service during the enthronement of Jayaatu Khan. The Khan rewarded him with the position of left chancellor along with countless gold and silver as well as privileges in the court.
In the conflicts about the succession of Jayaatu Khan Tugh Temür after 1332, Bayan broke with El Temür and supported Toghon Temür, who ascended the throne in 1333 (the same who would lose China in 1368). He was appointed commander of kheshig, composed of Mongols, Kypchaks, Russians and Asud in 1334. Until 1335 Bayan succeeded in annihilating El Temür's sons and family. Bayan began concentrating official positions in his person that had not been so concentrated before. He implemented rather conservative politics, abolishing the imperial examination system, and aimed to contain the number of Han Chinese in the upper echelons of the Yuan bureaucracy. He once suggested the emperor kill those Han Chinese of the more numerous surnames: Zhang, Wang, Liu, Li and Zhao to suppress the rebellion. In 1339 he became grand chancellor (Chinese: 大丞相; pinyin: dà chéngxiàng). At that time he had probably gone too far, in any case he was toppled in 1340 by his nephew Toqto'a. Shortly after that, his purges were called off and his policies were reversed.
According to the Chinese historians, Toqto expressed his share of woe to his father, saying that his uncle Bayan's authoritarian tendencies might bring disasters to his clan. On the other hand, Toghon Temür， the emperor, also began to worry about the exceedingly ostentatious power of Bayan. Wu Zhifang, a Confucian scholar in the court suggested Toqto to take action against Bayan. In the end, Bayan was removed from the central theatre of the imperial court.