He seized the throne in 430 when his brother Feng Ba (Emperor Wencheng) was ill, and he used the title "Heavenly King".
Probably also at the same time (but definitely during Gao Yun's reign), Feng Hong was created the Duke of Ji.
After Gao Yun was assassinated by his attendants Li Ban (離班) and Tao Ren (桃仁) in 409, the officials of the regime supported Feng Ba as the new emperor.
Only one of her trusted officials, Hu Fu (胡福), was able to enter the palace to be in charge of security.
However, Hu was secretly resentful of Consort Song's ambitions, and he informed Feng Hong of her intentions.
This appeared to be particularly true after Northern Wei annexed all of the territory of Xia in 431 and therefore no longer had a major western rival to deal with.
Feng Hong tried to appease the Northern Wei emperor by delivering gifts of beef and wine to his army, to no avail.
In spring 434, Feng Hong sent messengers to Northern Wei to request peaceful relations.
Because Feng Hong refused to send Feng Wangren, Emperor Taiwu again sent Tuoba Jian against Northern Yan, and Tuoba Jian seized Northern Yan's crops and some of its people before withdrawing.
Emperor Wen of Liu Song created Feng Hong the Prince of Yan, but was unable to provide substantial aid.
This reason appeared to have been rejected by Northern Wei, and Feng Hong again tried to seek Liu Song aid, but none was coming.
In summer 435, Emperor Taiwu's brother Tuoba Pi (拓拔丕) the Prince of Leping again arrived at Helong, and Feng Hong tried to appease him by offering cattle, wine, and armor, but Tuoba Pi's assistant general Qutu Yuan (屈突垣) accused Feng Hong of not sending hostages, and they seized 6,000 Northern Yan men and women before withdrawing.
Emperor Taiwu, not believing in Feng Hong, refused the overture and prepared another attack.
Because the people largely were weary about relocating to Goguryeo, the official Guo Sheng (郭生) opened the city gates and tried to surrender, but Northern Wei forces thought it was a trap and did not aid him, and Feng Hong killed Guo in battle.
However, King Jangsu seized Wang and sent him back to Liu Song, demanding that he be imprisoned, and Emperor Wen did so for a time before releasing him.