Ji Ben served as a Court Physician (太醫令) in the imperial court of the Eastern Han dynasty during the reign of Emperor Xian (). Around the time, the Han central government had fallen under the control of Cao Cao, the Imperial Chancellor. Emperor Xian was merely a figurehead ruler. In 216, Emperor Xian granted Cao Cao the title of a vassal king – King of Wei (魏王) – and allowed him to establish a vassal kingdom in northern China which was still nominally under the Han administration.