Xú Yì appellation Jìcái, was a Dōngguǎn man. He took refuge east of the Jiāng, and Sūn Cè sought to invite and recruit him. Yì changed his name and fled in disguise back to his home prefecture.
When Tàizǔ [Cáo Cāo] was Excellency of Works he was appointed to his staff. He followed in the western campaign against Mǎ Chāo . Chāo was defeated and the army returned. At that time the land within the Passes was newly taken and not yet at fully peace, so Yì was left as Chief Clerk to the Chancellor to defend and support the western capital [Cháng’ān], and there in the western capital he was praised and trusted. He was transferred to Inspector of Yōngzhōu, then returned [to headquarters] as Officer Assistant. At the time Dīng Yí and his group were in favor and they all hated and acted against him, but to the end Yì made no move [in response]. (1) He was transferred out to serve as Administrator of Wèi-jùn.
- (1) Wèishū states: Someone said to Yì: “You have Shǐyú’s uprightness, but what about Qú Bóyù’s wisdom? Dīng Yí is in high favor. You should think of this and so defer to him.” [Xú] Yì said: “With a wise and sagely lord, how can [Dīng] Yí and his deceptions last long? And I can defend against those who act treacherously, so let him plot against me.”
- Fù-zǐ states: Wǔ–dì [Cáo Cāo] had limits to his wisdom. Cuī Yǎn and Xú Yì were always pure and worthy, and both were loyal and sincere to the Wèi Court. Dīng Yí spoke against them, so Xú Yì lost his position while Cuī Yǎn was put to death.
When Tàizǔ attacked Sūn Quán, he transferred Yì to remain at headquarters as Chief Clerk and said to him: “Your loyalty and integrity is unsurpassed by the ancients, but you are a bit too strict. In the past Xīmén Bào wore a girdle to restrain himself, and so could act both with gentleness or hardness. I hope that you can be like this. Now I send you to remain to manage affairs, I will have no fears behind me.”
When Wèi state was established  he joined the Secretariat, served as an Elector, and was promoted to Director of the Secretariat.
While Tàizǔ campaigned in Hànzhōng, Wèi Fěng and others rebelled. Subaltern Yáng Jùn was sent east. Tàizǔ sighed and said: “The reason Fěng dared rebel was because among my followers there was none who can discover those with treacherous plans. If I could obtain someone like a Zhūgě Fēng, who can I send to Jùn?”
Huán Jiē said: “Xú Yì is your man.”
Tàizǔ therefore sent Yì as Subaltern, and hand wrote an order: “In the past Chǔ had Zǐyù, so Wén-gōng could not be at ease at his seat. When Jí Àn sat at Court, [the King of] Huáinán abandoned his treacherous plans. The Shī [jīng] tells of “one to manage a state,” and that is speaking of you!” He held the post for several moons, but because of serious illness resigned, was appointed Critical-Consultant Officer, but died. (1)
- Wèishū states: Wén-dì at every meeting with his ministers would never fail to sigh and think of Yì’s conduct. Yì had no sons, so an Imperial Order appointed his cousin’s son Tǒng as an official and as Yì’s posterity.