Bi Xian was born in 802, during the reign of Emperor Dezong. His family was originally from Yun Prefecture and originally claimed ancestry from Ji Gao, a son of King Wen of Zhou, who was created the Lord of Bi, although his traceable ancestry only went back to his fifth-generation ancestor, Bi Jing, who served as a prefectural prefect during Tang Dynasty. Bi Xian's grandfather Bi Jun served as a prefectural secretary general, while his father Bi Yun served as a musical scholar in the ministry of worship. Bi Xian lost his father early in life, and was poor in his childhood. However, he was said to be diligent, and he studied by burning wood and reading by the fire. After he was grown, he was well-studied in the Confucian classics and the histories, but was particularly capable in writing poetry.
During Emperors Wenzong's and Wuzong's reigns
Bi Xian passed the imperial examinations in the Jinshi class in the middle of the Taihe era of Emperor Dezong's great-great-grandson Emperor Wenzong, and he later passed a special imperial examination for those who made good rulings. Thereafter, when the official Du Cong served as the military governor of Zhongwu Circuit, Du invited Bi to serve as an assistant. When Du later served as the director of finances, Bi served as a traveling reviewer under him. Later, when Du served as the military governor of Huainan Circuit, he continued to serve on Du's staff. When Du was recalled to the capital Chang'an to serve as chancellor in 844 by then-reigning Emperor Wuzong, Bi returned to Chang'an as well and was made an imperial censor, initially with the title of Jiancha Yushi, then as Shi Yushi. At that time, however, another chancellor, Li Deyu, was the leading figure at court, and Li did not get along with Du. In 845, Du was therefore sent out of Chang'an to serve as the military governor of Dongchuan Circuit. Because Du had offended Li, his former subordinates largely did not dare to send Du off, but Bi did. Li, hearing this, was displeased, and sent Bi out of the capital to serve as the prefect of Ci Prefecture.
During Emperor Xuānzong's reign
After Emperor Wuzong died in 846 and was succeeded by his uncle Emperor Xuānzong, Li Deyu lost power, and many of those whom Li had demoted were promoted. Bi Xian was thereafter made Hubu Yuanwailang, a low-level official at the ministry of census, with his office at the eastern capital Luoyang. He was then recalled to Chang'an to serve as Jiabu Yuanwailang, a low-level official at the ministry of defense in charge of imperial messengers' horses and wagons, and then as Cangbu Langzhong, a supervisory official at the ministry of census in charge of imperial money and food storages. During those times, the Jiabu and Cangbu assignments were not considered honored assignments, and officials who were from prominent clans would be displeased if assigned to them, but Bi accepted them happily and respectfully, impressing the chancellors who assigned him. He was thereafter made Zhifang Langzhong, a supervisory official at the ministry of defense in charge of military maps, as well as supervisory censor. He was soon made an imperial scholar and Zhongshu Sheren, a mid-level official at the legislative bureau of government. As of 852, Emperor Xuānzong had to deal with frequent Dangxiang incursions on the northwest borders, and he was hoping to find a suitable military governor for Binning Circuit, but could not find one. On one occasion, when he discussed with Bi what proper border policies should be, Bi discussed the history and listed a number of suggestions that he had. Emperor Xuānzong was impressed, compared him to the prominent Zhao generals Lian Po and Li Mu, and asked him whether he would be willing to accept the Binning assignment. Bi agreed cheerfully. Emperor Xuānzong, in order to increase his prominence before sending him out on assignment, first made him the deputy minister of defense, then made him the military governor of Binning. Later that year, he reported that the Dangxiang troubling Binning had all been pacified. That allowed Binning's headquarters, which had been temporarily moved from Bin Prefecture to Ning Prefecture due to the Dangxiang incursions, to be returned to Bin Prefecture in spring 855. It was said that while at Binning, Bi encouraged the soldiers to tend the fields and grow crops for the military food supplies, allowing them to be supplied adequately at a reduced cost to the imperial treasury. He was later transferred to Zhaoyi Circuit and then Hedong Circuit. As Hedong was on the border, Bi established 70 watch posts to defend against attacks. However, while it was said that Emperor Xuānzong had previously promised him that he would be recalled to serve as chancellor, then-lead chancellor Linghu Tao was fearful of him, and therefore he was never recalled during that timespan.
During Emperor Yizong's reign
Emperor Xuānzong died in 859 and was succeeded by his son Emperor Yizong. Thereafter, Bi Xian was transferred to Xuanwu Circuit, and yet later recalled to Chang'an to serve as the minister of census as well as the director of finances. In 860, Emperor Yizong made him the minister of rites and gave him the designation Tong Zhongshu Menxia Pingzhangshi, making him a chancellor de facto. As chancellor, he was said to be a capable administrator and talented in his writing. He served as a chancellor until 863, when he resigned his chancellor post, ostensibly due to illness, but was said to have actually resigned because he was unhappy that his chancellor colleagues did not uphold the law properly. He was thereafter made the minister of defense. He was thereafter made the military governor of Hezhong Circuit, and died two months later, in early 864.
