He came from Jinan 濟南 (modern Jinan, Shandong) and was once punished by castration yet then appointed palace attendant (zhonghuangmen 中黃門). Later on he succeeded Hong Gong 弘恭 in the office as Director of the Imperial Secretariat (zhongshu ling 中書令). When Emperor Yuan 漢元帝 (r. 49-33 BCE) fell ill, virtually all political matters were decided by Shi Xian so that all ministers at the court accepted his superior role in government.
Grand minister Xiao Wangzhi 蕭望之 saw the empire threatened by the powerful role Shi Xian played and remonstranted against him. Yet Emperor Yuan did not pay attention to Xiao's warning so that the general was forced to kill himself.
When Emperor Cheng 漢成帝 (r. 33-7 BCE) mounted the throne Shi Xian was appointed Chamberlain for the Imperial Stud (taipu 太僕) of the Changxin Palace 長信宮, a position in which he had no influence any more on political decisions. This was the chance for the highest ministers in the government to accuse him of moral obliquity. Shi Xian was dismissed and sent back to his home town, yet he died during the journey home by self-starvation.