After his son Murong Jun completely broke away from the Eastern Jin and claimed the title of emperor in January 353, he was posthumously elevated to imperial status.
During Murong Hui's rule as tribal chief, the Jin dynasty's central government was in constant turmoil and eventually collapsed due to infighting and agrarian rebellions, the strongest of which was the Xiongnu state Han-Zhao.
As a result, many refugees arrived in the relatively safe domain of Murong Hui's, and as he treated the ethnically Han refugees with kindness, most chose to stay, greatly strengthening his power, and as Jin forces in the north gradually fell to Han-Zhao's capable general Shi Le (who later established his own independent state Later Zhao), Murong Hui became the only domain in northern China still under titular Jin rule, carrying the Jin-bestowed title of the Duke of Liaodong.
Murong Huang took over his administration under the Jin-bestowed office of General Pingbei (平北將軍) and sent messengers to report his father's death to Emperor Cheng of Jin and request commission official for himself.
Soon after, with Jin commission expected but not yet arrived, he claimed the title of Duke of Liaodong, which his father had carried.
Duan Lan wanted to further advance on Jicheng, but Murong Han, fearful that his own tribe would be destroyed, ordered a withdrawal.
He then withdrew, and when Later Zhao forces arrived, Duan Liao no longer dared to face them but instead abandoned Lingzhi and fled.
Murong Huang considered fleeing, but under advice of his general Muyu Gen, he stayed and defended the city for nearly 20 days, and Later Zhao forces were forced to withdraw; Murong Huang then sent his son Murong Ke to attack the retreating Later Zhao troops, scoring a great victory, and the only Later Zhao force remaining intact was that of Shi Min, Shi Hu's adopted grandson.
Also in 339, Murong Huang married his sister to Tuoba Shiyiqian, the Prince of Dai, cementing an alliance between the two Xianbei powers.
In 341, after several months of debate, Emperor Cheng decided to grant Murong Huang the princely title.
In 341, Murong Huang moved his capital from Jicheng to a newly built city, Longcheng (龍城, in modern Zhaoyang, Liaoning).
In 345, Murong Huang stopped using Jin's era names—which is viewed by some as the sign of Former Yan's formal independence.