By 384, he was the governor of Pingyang Commandery (平陽, roughly modern Linfen, Shanxi).
When he heard that his uncle Murong Chui and his older brother Murong Hong had rebelled against Former Qin in light of Fu Jiān's defeat at the Battle of Fei River in 383, he rebelled as well.
He was soon defeated by the Former Qin general Dou Chong, and he joined his brother Murong Hong.
Upon hearing news of his brother's death, Murong Chong declared himself emperor.
Despite his Xianbei people's desire to return east to their homeland, Murong Chong decided to settle in Chang'an—both because he liked the city and because he feared his uncle Murong Chui, who had by then established Later Yan.