He is a member of the National Assembly and served as the Floor Leader of the Justice Party.

Yun joined the Mokpo Youth Union in 1985; a social movement that advocated for an end to the regime of Chun Doo-hwan.

[3] In 2008, Yun ran for representative of Mokpo under the Democratic Labor Party, he came in third place.

He plans to run for representative of Mokpo in the upcoming 2020 South Korean legislative election.

[4] Due to death of Roh Hoe-chan in 2018, Yun assumed the position of acting Floor Leader of the Justice Party.