His mother was Liu Yu's concubine Consort Wang, who later carried the rank Xiurong (修容).
His involvement in government service started in 420, when Liu Yu, on the verge of usurping the Jin throne, left his post at Shouyang (壽陽, in modern Lu'an, Anhui) and made Liu Yikang titularly in charge of Shouyang as the governor of Yu Province (豫州, modern central Anhui and southeastern Henan).
In 426, after Emperor Wen had defeated and killed Xie Hui the governor of the important Jing Province (荊州, modern Hubei), for having deposed and killed his older brother Emperor Shao in 424, he made Liu Yikang the governor of Jing Province to replace Xie.
The prime minister Wang Hong, who had tried to avoid having too much power, therefore offered to resign and have the post be given to Liu Yikang.
He also set up a guard corps of 6,000 men without getting prior approval, and did not see that it was inappropriate for him to accept gifts from other officials—gifts that were even more exquisite than the ones Emperor Wen received.
He then removed Liu Yikang from his post as prime minister and made him the governor of Jiang Province (江州, modern Jiangxi and Fujian), but put him under close watch by trusted generals, although he permitted Liu Yikang's staff members who were willing to accompany him to go to Jiang Province with him, and supplied him with many things.
However, in 451, in the middle of a Northern Wei invasion, Emperor Wen became apprehensive that conspirators might again try to use Liu Yikang as a focal point.