In 221, Liu Bei attacked his former ally, Sun Quan (the founding emperor of Eastern Wu), after the latter broke their alliance and seized his territories in Jing Province and executed his general Guan Yu. Feng Xi participated in this campaign, which led to the Battle of Xiaoting (or Battle of Yiling) of 221–222. In the initial stages of the battle, Feng Xi and Wu Ban defeated Sun Quan's officers Li Yi (李異) and Liu E (劉阿) in the area near the Wu Gorge and pressed further towards Zigui. Feng Xi was then appointed as the Grand Viceroy (大督) of the Shu army. In the summer of 222, Sun Quan's forces, led by Lu Xun, suddenly launched a counter-attack after about six months of stalemate since the beginning of 222. Feng Xi was killed in battle by the subordinates of the Wu general Pan Zhang and his unit suffered heavy casualties.
The Shu writer Yang Xi (楊戲) attributed Feng Xi's downfall to his overconfidence and underestimation of the enemy.