Zhu Yi's father Zhu Xuanzhi was known for his integrity, but was only a county magistrate at the prime of his career. Zhu Yi himself, when young, became known for his knowledge of the Confucian classics, history, and astrology. When he met Emperor Wu's minister Shen Yue, Shen was impressed by him, and although Zhu was not yet at the age of 24, which was generally required for junior Liang officials, Zhu was selected as an official at age 20, in 503. That year, he was selected to publicly pronounce Emperor Wu's commentaries on the ''Xiao Jing'' -- an honor for junior officials -- and from that point, he was repeatedly promoted. This was particularly the case after 524, when Zhu correctly judged that the rival Northern Wei's general Yuan Faseng was truly surrendering his garrison of Pengcheng to Liang. That year, one of Emperor Wu's co-de facto prime ministers, Zhou She, died, and after Zhou's death Zhu became increasingly involved in drafting edicts for Emperor Wu and in making judgment in some important matters. He was described to be quick in his reactions, getting work done quickly. After Xu Mian's death in 535, Zhu became de facto prime minister, although he never carried that title. By this point, Zhu was considered to be capable but corrupt, often accepting large bribes and then making recommendations to Emperor Wu based on those bribes. The historian Sima Guang commented about Zhu in this manner in his ''Zizhi Tongjian'':
:''Zhu was spectacular in his writing talent, and for his quick and proper reactions. He used all his effort to build up his reputation among the people. Zhu carefully served the emperor, and was good at flattering. He spent 30 years in power, and he was exceedingly corrupt, deceiving and covering the eyes of the emperor. The people of the entire empire, regardless of how far they were from the capital, hated him greatly. Zhu's garden, residence, favorite items, food, entertainment, and women were all best in the empire. Whenever he had a vacation and returned to his home, the streets were filled with the wagons of his guests.''
In 547, the Eastern Wei general Hou Jing, not willing to submit to Gao Cheng, the son of the paramount general Gao Huan after Gao Huan's death, surrendered his domain -- 13 provinces forming the region between the Huai River and the Yellow River -- to Liang. Emperor Wu initially hesitated at accepting Hou's defection, given his long-standing peace with Eastern Wei, but Zhu, seeing how deep in his heart Emperor Wu wanted more territory, greatly encouraged him to accept Hou. However, both Hou and the army Emperor Wu sent to support Hou, commanded by Emperor Wu's nephew Xiao Yuanming the Marquess of Zhenyang, were defeated by the Eastern Wei general Murong Shaozong . Xiao Yuanming was captured by Murong, while Hou lost his entire territory. Emperor Wu made Hou the governor of Southern Yu Province , but at Zhu's suggestion, entered into peace talks with Eastern Wei. Hou became apprehensive, and he paid a large bribe to Zhu to ask Zhu to stop the peace talks. Zhu accepted Hou's bribes but refused to intercede. At the same time, not taking Hou seriously, Zhu rejected warnings from Emperor Wu's nephew Xiao Fan the Prince of Poyang to prepare for a Hou rebellion. Soon, Hou was suspicious that he would be betrayed, and he forged a letter from Gao Cheng, offering to trade Xiao Yuanming for Hou. Emperor Wu, after Zhu convinced him that Hou posed no actual threat, accepted -- and when Hou saw this, he rebelled in 548, claiming that he was seeking to clear the court of evil officials -- Zhu, along with Xu Lin , Lu Yan , and Zhou Shizhen . Even then, Zhu did not take Hou seriously, and when the general Yang Kan suggested blocking Hou's path to the Yangtze River, Zhu advised against it, and Emperor Wu did not do so, allowing Hou to cross the Yangtze easily and put the capital Jiankang under siege.
During the siege, Hou again repeatedly stated that he was only seeking to execute Zhu. When Emperor Wu asked his crown prince whether the crimes that Hou accused Zhu of were true, Xiao Gang indicated that they were true -- but subsequently spoke against Emperor Wu's thought of executing Zhu, arguing that doing so would only encourage Hou. Zhu was therefore spared, and subsequently participated in the city's defense, and he wrote letters to Hou trying to persuade Hou to lift the siege, to no avail. When Hou's general Fan Taobang subsequently offered to defect and kill Hou, Zhu greatly advocated for the plan, but Xiao Gang suspected Fan's intentions and therefore did not act on the offer.
The people of the capital all believed that Hou's rebellion was stoked by Zhu's corruption. Zhu, in embarrassment and fear, became ill. He died in 549, with the city still under siege. Emperor Wu, still believing in his faithfulness, buried him with honor.