He was confirmed as heir to the throne in 533, the third year of Anwon's reign. Although he was the heir, it is said that he was not able to simply assume power after his father's death. Anwon had three wives, and because the first did not bear him a son, the other queens strove to put their son on the throne. Yangwon's supporters won the military struggle and he was able to succeed to the throne.[2][3]
Preparing for war in 547, Yangwon rebuilt Baegam fortress and repaired Sin fortress. In 548, he sent 6,000 soldiers against Baekje's Doksan Fortress but the Silla general Ju Jin led a relief army and the Goguryeo assault failed. In 550, Baekje invaded and sacked Dosal fortress. Goguryeo counterattacked and struck Baekje's Geumhyeon fortress, but Silla took advantage of this to seize two more Goguryeo castles.
In 551, the emerging empire of the Göktürks invaded from Central Asia[1] and laid siege to Sin fortress; unable to take it, they attacked Baegam fortress instead. At this, Yangwon sent his general Go Heul and 10,000 troops against the Göktürks; they killed or captured 1,000. In the same year, Silla invaded once again and captured ten districts of the present-day Seoul region.[2] In 552, Jangan fortress was built. In 554, Yangwon's forces attacked Ungcheon fortress in Baekje, but failed to take it.
In 553, Northern Qi's Emperor Wenxuan sent ambassador Cui Liu to Goguryeo to request the return of Chinese civilians who had fled the turmoil during the end of Northern Wei. When Yongwon's court refused, Cui Liu became furious and punched Yangwon off his chair. Frightened, Yangwon apologised for refusing and agreed to return five thousand households.
In 557, Yangwon designated the prince Go Yang-seong as heir to the throne. In the tenth lunar month of that same year, the commander Gan Juri of Hwando fortress rebelled, but the rebellion was put down and he was executed. Yangwon died in 559, after fifteen years on the throne.