He originally served under Liu Zhang, the Governor of Yi Province (covering present-day Sichuan and Chongqing), as the Prefect of Mianzhu County (綿竹縣).
Around 219, after Liu Bei declared himself King of Hanzhong, he tasked Fei Shi with travelling to Jing Province to inform Guan Yu about his appointment as General of the Vanguard (前將軍).
However, when Guan Yu learned that Huang Zhong would server as the General of the Rear (後將軍), he angrily said, "I would never allow myself to share the same rank as this old soldier!".
Fei Shi, in order to convince Guan Yu, said to him :“When one is looking to realize a hegemon's ambitions, he cannot have a one-track mind and must embrace multiple possibilities.
He argued that Liu Bei should not declare himself emperor until he had vanquished Shu's rival state, Cao Wei, which replaced the Eastern Han dynasty in 220; he cited the example of Liu Bang, the founder of the Han dynasty, who only declared himself emperor after defeating his rival Xiang Yu in the Chu–Han Contention.
[5] Liu Bei was so displeased that he had Fei Shi demoted to serve as a low-ranking official in Yongchang Commandery (永昌郡) in the remote southern parts of Shu.
[6] Xi Zuochi, with regards to Fei Shi's outspoken and perhaps too honest opposition, commented: "Before establishing himself, a monarch must await the perfect conditions to lay the foundations for his state.
Accepting succession and honoring the Heavens: how could this compare with Xiang Yu and how could Liu Bei refuse to take the now vacant throne?
With this, Liu Bei could honor the previous emperors and with his example encourage others, unite his people toward a common goal which was the restoration of the Han and the destruction of the rebels.
[10] When he heard of this, Zhuge Liang told Jiang Wan and Fei Shi to return to the capital and start exchanging letters with Meng Da.
Unfortunately Master Meng, this was truly Liu Feng's fault for offending you and so harming Xianzhu's reputation of treating scholars with respect.
I also heard from Li Hong that Wang Chong spread lies, but you answered that you knew my feelings and so refused to believe him.
Due to the swift actions of Sima Yi and because he doubted the sincerity of Meng Da, Zhuge Liang did not rescue him.
He was appointed as a Counsellor Remonstrant (諫議大夫) sometime after Zhuge Liang's death in 234, when Jiang Wan was the head of government in Shu.